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# Java lesson 30

2022-04-29 06:11:00【Yake1965】

# 1897. Reassign characters so that all strings are equal

# Basic knowledge of

### The first 30 course

- 1897. Reassign characters so that all strings are equal
- Basic knowledge of
- 1331. Array number conversion
- 1002. Find common characters
- Basic knowledge of
- 914. Card groups
- 904. Fruit baskets
- [781. Rabbits in the forest ](https://leetcode-cn.com/problems/rabbits-in-forest/)
- Basic knowledge of
- [648. Word substitution ](https://leetcode-cn.com/problems/replace-words/)
- 389. Make a difference
- *1700. Number of students unable to have lunch
- Basic knowledge of
- 229. Find mode II
- 1365. How many numbers are smaller than the current number
- 888. Fair candy exchange
- 1452. Collection list
- Basic knowledge of
- 383. Ransom letter
- 997. Find the judge in town
- 229. Find mode II
- 575. Divide candy
- [1054. Bar codes with equal distances ](https://leetcode-cn.com/problems/distant-barcodes/)
- 560. And for K Subarray
- [41. First positive number missing ](https://leetcode-cn.com/problems/first-missing-positive/)
- 242. Effective alphabetic words
- 244. The shortest word distance II
- 246. Centrosymmetric number
- 249. Shift string grouping
- 264. Ugly number II
- 266. Palindrome arrangement
- 267. Palindrome arrangement II
- 268. Missing numbers
- 76. Minimum cover substring
- 288. The only abbreviation of a word
- [290. Rules of words ](https://leetcode-cn.com/problems/word-pattern/)
- 291. Rules of words II
- 299. Guess the number game
- 3. Longest substring without repeating characters
- 30. Concatenate the substrings of all words
- 311. Multiplication of sparse matrices
- 313. Super ugly number
- 314. Vertical traversal of binary trees
- 325. And equal to k The longest subarray length of
- 336. The palindrome is right
- 340. At most K Longest substring of different characters
- 347. front K High frequency elements
- 348. Design tic tac toe chess
- 349. Intersection of two arrays
- 350. Intersection of two arrays II
- 355. Design twitter
- 356. Line mirror image
- 358. K The distance interval rearranges the string
- 359. Log rate limiter
- 36. Effective Sudoku
- 362. Hit the counter
- 379. Telephone directory management system
- 380. O(1) Time insertion 、 Delete and get random elements
- 381. O(1) Time insertion 、 Delete and get random elements - Allow repetition
- 387. The first unique character in the string
- 395. There are at least K The longest substring of repeated characters
- 398. Random number index
- 409. Longest palindrome
- 421. The maximum exclusive or value of two numbers in an array
- 423. Reconstructing Chinese from English
- 424. The longest repeated character after replacement
- 432. whole O(1) Data structure of
- 433. Minimal genetic change
- 438. Find all alphabetic words in the string
- 442. Duplicate data in array
- 447. The number of boomerangs
- 448. Find all the missing numbers in the array
- 451. Sort the characters according to their frequency of occurrence
- 454. Add four numbers II
- 457. Whether there is a loop in the ring array
- 460. LFU cache
- 480. Sliding window median
- 49. Letter heterotopic word grouping
- 491. Increasing subsequence
- 496. Next bigger element I
- 500. Keyboard line
- 508. The most frequent sub tree elements and
- 519. Random flip matrix
- 522. The longest special sequence II
- 523. Continuous subarrays and
- 531. Lonely pixels I
- 532. Array k-diff Number pair
- 533. Lonely pixels II
- 535. TinyURL Encryption and decryption
- 567. Arrangement of strings
- 582. Kill the process
- 588. Design memory file system
- 594. The longest harmonious subsequence
- 599. The minimum index sum of two lists
- 604. Iteratively compress strings
- 609. Find duplicate files in the system
- 616. Add bold tags to strings
- 621. Task scheduler
- 632. Minimum range
- 635. Design the log storage system
- 645. The wrong set
- 652. Look for duplicate subtrees
- 653. Sum of two numbers IV - Input BST
- 659. Split the array into successive subsequences
- 676. Implement a magic dictionary
- 677. Key value mapping
- 690. The importance of employees
- 692. front K High frequency words
- 694. The number of different islands
- 697. The degree of the array
- 705. Design hash sets
- 706. Design hash map
- 710. Random numbers in the blacklist
- 711. The number of different islands II
- 720. The longest word in the dictionary
- 726. The number of atoms
- 73. Matrix zeroing
- 734. Sentence similarity
- 736. Lisp Syntax parsing
- 737. Sentence similarity II
- 740. Delete and get points
- 748. The shortest complement
- 752. Open the turntable lock
- 758. Bold words in strings
- 760. Find the displacement map
- 763. Division of alphabet
- 767. Refactoring strings
- 770. Basic calculator IV
- 771. Gems and stones
- 791. Custom string sorting
- 792. Number of words to match subsequence
- 804. The only Morse code word
- 811. Subdomain access count
- 815. Bus routes
- 817. Linked list component
- 819. The most common word
- 820. Compression coding of words
- 822. Flip card game
- 823. Binary trees with factors
- 859. Intimate string
- 865. The smallest subtree with all the deepest nodes
- 868. Binary spacing
- 873. The length of the longest Fibonacci subsequence
- 884. Unusual words in two sentences
- 889. Construct binary tree according to preorder and postorder traversal
- 890. Find and replace patterns
- 893. Special equivalent string group
- 895. Maximum frequency stack
- 911. Online elections
- 916. Word subsets
- 923. Many possibilities of the sum of three
- 929. Unique email address
- 930. And the same binary subarray
- 939. Minimum area rectangle
- 953. Verification of an alien language dictionary
- 954. Double pair array
- 957. N After the day of
- 961. In length 2N Find duplicates in the array of N Secondary elements
- 966. Vowel spelling checker
- 970. Strong integer
- 974. And can be K A subarray of integers
- 981. Time based key value storage
- 982. A triple with a bitwise and zero
- 987. The vertical traversal of a binary tree
- 992. K Sub array of different integers
- 1001. Grid lighting
- 1002. Find common characters
- 1010. The total duration can be 60 The song of division
- 1015. Can be K The smallest integer that is divisible
- 1027. The longest arithmetic sequence
- 1036. Escape the maze
- 1048. The longest string chain
- 105. Construction of binary trees from traversal sequences of preorder and middle order
- 106. Construct binary tree from middle order and post order traversal sequence
- 1072. Flip by column to get the maximum number of equal rows
- 1074. The sum of the elements is the number of submatrixes of the target value
- 1086. The average score of the top five subjects
- 1090. The maximum value affected by the tag
- 1100. The length is K There is no repetition in the string
- 1122. Relative sorting of arrays
- 1123. The closest common ancestor of the deepest leaf node
- 1124. The longest period of good performance
- 1128. Number of equivalent domino pairs
- 1133. Maximum unique number
- 1138. The path on the letterboard
- 1146. Snapshot array
- 1152. Analysis of user's website visiting behavior
- 1153. String conversion
- 1160. spell the words
- 1165. Single keyboard
- 1166. Designing a file system
- 1169. Query invalid transactions
- 1170. Compare the frequency of the smallest letter in a string
- 1171. Delete consecutive nodes with zero sum from the linked list
- 1172. Plate stack
- 1177. Construct palindrome string detection
- 1178. Guess the riddle
- 1181. Front and back stitching
- 1189. “ balloon ” Maximum number of
- 1198. Find the smallest common element in all rows
- 12. Integer to Roman number
- 1202. Exchange elements in a string
- 1207. Unique occurrences
- 1213. The intersection of three ordered arrays
- 1218. The longest definite difference subsequence
- 1224. Maximum equal frequency
- 1244. To make the best of the rankings
- 1248. Statistics 「 Graceful subarray 」
- 1257. The smallest common area
- 1258. Synonym sentence
- 126. The word chain II
- 1261. Look for elements in the contaminated binary tree
- 127. The word chain
- 1275. Find out the winner of tic tac toe
- 128. The longest continuous sequence
- 1282. User groups
- 1296. Divide an array into a set of consecutive numbers
- 1297. The maximum number of substrings
- 13. Roman numeral to integer
- 1311. Get videos your friends have watched
- 133. Clone map
- 1331. Array number conversion
- 1338. Halve the size of the array
- 1345. Jumping game IV
- 1346. Check the existence of integers and their multiples
- 1347. The minimum number of steps to make heterotopic words
- 1348. Tweet count
- 1357. every other n A discount for one customer
- 1358. The number of substrings containing all three characters
- 1365. How many numbers are smaller than the current number
- 1366. Rank the team by voting
- 1370. Up down string
- 1371. Each vowel contains an even number of times the longest substring
- 138. Copy list with random pointer
- 1386. Seating the cinema
- 139. Word splitting
- 1394. Find the lucky number in the array
- 1396. Design the subway system
- 1399. Count the number of the largest groups
- 140. Word splitting II
- 1400. structure K Palindrome strings
- 141. Circular list
- 1410. HTML Entity Resolver
- 1418. Order display form
- 142. Circular list II
- 1426. Number elements
- 1429. The first number
- 1436. Travel terminal
- 1442. The number of triples that form two exclusive or equal arrays
- 1443. The minimum time to collect all the apples on the tree
- 146. LRU cache
- 1460. Make two arrays equal by flipping the rotor array
- 1461. Check whether a string contains all the length of K The binary substring of
- 1477. Find two non overlapping subarrays whose sum is the target value
- 1481. The minimum number of different integers
- 1485. Clone a binary tree with random pointers
- 1487. Make sure the file name is unique
- 1488. Avoid flooding
- 149. The most points on the line
- 1490. clone N Fork tree
- 1496. Determine whether the paths intersect
- 1497. Check whether array pairs can be k to be divisible by
- 1500. Design document sharing system
- 1506. find N The root node of the fork tree
- 1512. A good number of pairs
- 1519. The number of nodes with the same label in the subtree
- 1540. K Operations change string
- 1542. Find the longest favorite substring
- 1546. The maximum number of non empty subarrays with and as the target value and without overlapping
- 1554. A string with only one different character
- 1570. Dot product of two sparse vectors
- 1577. The square of a number is equal to the method number of the product of two numbers
- 159. The longest substring containing at most two different characters
- 1590. Make arrays and can be P to be divisible by
- 1593. Split the string to maximize the number of unique substrings
- 160. Intersecting list
- 1600. The order of succession to the throne
- 1604. Warn people who use the same employee card more than three times in an hour
- 1624. The longest substring between two identical characters
- 1636. Sort the array in ascending order by frequency
- 1638. Count the number of substrings with only one character difference
- 1640. Can you join to form an array
- 1650. The nearest common ancestor of a binary tree III
- 1656. Design ordered flow
- 1657. Determine whether two strings are close to
- 1658. take x Reduced to 0 Minimum operands of
- 166. Fractions to decimals
- 1660. Correct binary tree
- 1674. The minimum number of operations to make arrays complementary
- 1679. K The maximum number of sum pairs
- 1684. Count the number of consistent strings
- 169. Most elements
- 1695. Delete the maximum score of the subarray
- 17. Letter combination of telephone number
- 170. Sum of two numbers III - Data structure design
- 1711. Big meal count
- 1713. Get the minimum number of operations of subsequence
- 1726. Coproduct tuple
- 1737. The minimum number of characters to be changed to satisfy one of the three conditions
- 1740. Find the distance in the binary tree
- 1742. The maximum number of balls in the box
- 1743. Restore an array from a pair of adjacent elements
- 1748. The sum of the only elements
- 1756. Design recently used （MRU） queue
- 1763. The longest nice substring
- 1772. Rank functions by popularity
- 1775. Make the sum of arrays equal by the least number of operations
- 1781. The sum of all substrings
- 1790. Can performing only one string exchange make two strings equal
- 1794. Count the number of substring pairs with the smallest distance
- 1796. The second largest number in a string
- 1797. Design a verification system
- 1804. Realization Trie （ Prefix tree ） II
- 1805. The number of different integers in a string
- 1807. Replace the parentheses in the string
- 1814. Count the number of good pairs in an array
- 1817. Find user active minutes
- 1832. Judge whether the sentence is a full letter sentence
- 1836. Remove duplicate elements from the unsorted linked list
- 1852. The number of types of numbers in each subarray
- 1857. The maximum color value in a directed graph
- 1865. Find the subscript pair for the specified value
- 187. Repetitive DNA Sequence
- 1876. Substrings of three different characters
- 1893. Check that all integers in the region are overwritten
- 1897. Reassign characters so that all strings are equal
- 1906. The minimum value of the absolute value of the query difference
- 1912. Design movie rental system
- 1915. The number of most beautiful substrings
- 1930. The length is 3 Different palindrome subsequences
- 1932. Merge multiple binary search trees
- 1935. The maximum number of words that can be entered
- 1940. Sort the longest common subsequence between arrays
- 1941. Check that all characters appear the same number of times
- 1948. Delete duplicate folders in the system
- 1993. Operations on the tree
- 2001. Number of groups of interchangeable rectangles
- 2006. The absolute value of the difference is K Number to number
- 2007. Restore the original array from the double array
- 2013. Detection square
- 202. Happy number
- 2025. The maximum number of schemes to split the array
- 2032. Values that appear in at least two arrays
- 2034. Stock prices fluctuate
- 2043. Simple banking system
- 205. Isomorphic Strings
- 2053. No K A unique string
- 2062. Count the vowel substrings in the string
- 2068. Check that the two strings are almost equal
- 208. Realization Trie ( Prefix tree )
- 2080. The frequency of querying numbers in the interval
- 2083. Find the total number of substrings beginning and ending with the same letter
- 2085. Count the public strings that appear once
- 2094. find 3 Bit even
- 2099. Find and the maximum length is K The subsequence
- 2103. Ring and rod
- 2107. Share K The number of unique flavors after a candy
- 2115. Find all the dishes you can make from a given raw material
- 2121. The sum of the intervals of the same elements
- 2122. Restore the original array
- 2131. The longest palindrome string obtained by connecting two letter words
- 2133. Check whether each row and column contains all integers
- 2135. Count the number of words you can get by adding letters
- 2150. Find all the numbers in the array
- 2152. The minimum number of lines required to pass through all points
- 2154. Multiply the found value by 2
- 2166. Design bit set
- 2168. The number of unique substrings with the same frequency for each number
- 217. There are duplicate elements
- 2170. The minimum number of operands to make an array an alternating array
- 2186. The minimum number of steps to make two strings into alphabetic ectopic words
- 219. There are duplicate elements II
- 2190. Immediately following in the array key Then the most frequent number
- 2196. Create a binary tree according to the description
- 2201. Statistics of the artifacts that can be extracted
- 2206. Divide the array into equal pairs
- 2215. Find out the difference between the two arrays
- 2225. Find the player who lost zero or one game
- 2227. Encrypt and decrypt strings
- 2244. The minimum number of rounds required to complete all tasks

# 1331. Array number conversion

# 1002. Find common characters

# Basic knowledge of

### The first 31 course

- 1897. Reassign characters so that all strings are equal
- Basic knowledge of
- 1331. Array number conversion
- 1002. Find common characters
- Basic knowledge of
- 914. Card groups
- 904. Fruit baskets
- [781. Rabbits in the forest ](https://leetcode-cn.com/problems/rabbits-in-forest/)
- Basic knowledge of
- [648. Word substitution ](https://leetcode-cn.com/problems/replace-words/)
- 389. Make a difference
- *1700. Number of students unable to have lunch
- Basic knowledge of
- 229. Find mode II
- 1365. How many numbers are smaller than the current number
- 888. Fair candy exchange
- 1452. Collection list
- Basic knowledge of
- 383. Ransom letter
- 997. Find the judge in town
- 229. Find mode II
- 575. Divide candy
- [1054. Bar codes with equal distances ](https://leetcode-cn.com/problems/distant-barcodes/)
- 560. And for K Subarray
- [41. First positive number missing ](https://leetcode-cn.com/problems/first-missing-positive/)
- 242. Effective alphabetic words
- 244. The shortest word distance II
- 246. Centrosymmetric number
- 249. Shift string grouping
- 264. Ugly number II
- 266. Palindrome arrangement
- 267. Palindrome arrangement II
- 268. Missing numbers
- 76. Minimum cover substring
- 288. The only abbreviation of a word
- [290. Rules of words ](https://leetcode-cn.com/problems/word-pattern/)
- 291. Rules of words II
- 299. Guess the number game
- 3. Longest substring without repeating characters
- 30. Concatenate the substrings of all words
- 311. Multiplication of sparse matrices
- 313. Super ugly number
- 314. Vertical traversal of binary trees
- 325. And equal to k The longest subarray length of
- 336. The palindrome is right
- 340. At most K Longest substring of different characters
- 347. front K High frequency elements
- 348. Design tic tac toe chess
- 349. Intersection of two arrays
- 350. Intersection of two arrays II
- 355. Design twitter
- 356. Line mirror image
- 358. K The distance interval rearranges the string
- 359. Log rate limiter
- 36. Effective Sudoku
- 362. Hit the counter
- 379. Telephone directory management system
- 380. O(1) Time insertion 、 Delete and get random elements
- 381. O(1) Time insertion 、 Delete and get random elements - Allow repetition
- 387. The first unique character in the string
- 395. There are at least K The longest substring of repeated characters
- 398. Random number index
- 409. Longest palindrome
- 421. The maximum exclusive or value of two numbers in an array
- 423. Reconstructing Chinese from English
- 424. The longest repeated character after replacement
- 432. whole O(1) Data structure of
- 433. Minimal genetic change
- 438. Find all alphabetic words in the string
- 442. Duplicate data in array
- 447. The number of boomerangs
- 448. Find all the missing numbers in the array
- 451. Sort the characters according to their frequency of occurrence
- 454. Add four numbers II
- 457. Whether there is a loop in the ring array
- 460. LFU cache
- 480. Sliding window median
- 49. Letter heterotopic word grouping
- 491. Increasing subsequence
- 496. Next bigger element I
- 500. Keyboard line
- 508. The most frequent sub tree elements and
- 519. Random flip matrix
- 522. The longest special sequence II
- 523. Continuous subarrays and
- 531. Lonely pixels I
- 532. Array k-diff Number pair
- 533. Lonely pixels II
- 535. TinyURL Encryption and decryption
- 567. Arrangement of strings
- 582. Kill the process
- 588. Design memory file system
- 594. The longest harmonious subsequence
- 599. The minimum index sum of two lists
- 604. Iteratively compress strings
- 609. Find duplicate files in the system
- 616. Add bold tags to strings
- 621. Task scheduler
- 632. Minimum range
- 635. Design the log storage system
- 645. The wrong set
- 652. Look for duplicate subtrees
- 653. Sum of two numbers IV - Input BST
- 659. Split the array into successive subsequences
- 676. Implement a magic dictionary
- 677. Key value mapping
- 690. The importance of employees
- 692. front K High frequency words
- 694. The number of different islands
- 697. The degree of the array
- 705. Design hash sets
- 706. Design hash map
- 710. Random numbers in the blacklist
- 711. The number of different islands II
- 720. The longest word in the dictionary
- 726. The number of atoms
- 73. Matrix zeroing
- 734. Sentence similarity
- 736. Lisp Syntax parsing
- 737. Sentence similarity II
- 740. Delete and get points
- 748. The shortest complement
- 752. Open the turntable lock
- 758. Bold words in strings
- 760. Find the displacement map
- 763. Division of alphabet
- 767. Refactoring strings
- 770. Basic calculator IV
- 771. Gems and stones
- 791. Custom string sorting
- 792. Number of words to match subsequence
- 804. The only Morse code word
- 811. Subdomain access count
- 815. Bus routes
- 817. Linked list component
- 819. The most common word
- 820. Compression coding of words
- 822. Flip card game
- 823. Binary trees with factors
- 859. Intimate string
- 865. The smallest subtree with all the deepest nodes
- 868. Binary spacing
- 873. The length of the longest Fibonacci subsequence
- 884. Unusual words in two sentences
- 889. Construct binary tree according to preorder and postorder traversal
- 890. Find and replace patterns
- 893. Special equivalent string group
- 895. Maximum frequency stack
- 911. Online elections
- 916. Word subsets
- 923. Many possibilities of the sum of three
- 929. Unique email address
- 930. And the same binary subarray
- 939. Minimum area rectangle
- 953. Verification of an alien language dictionary
- 954. Double pair array
- 957. N After the day of
- 961. In length 2N Find duplicates in the array of N Secondary elements
- 966. Vowel spelling checker
- 970. Strong integer
- 974. And can be K A subarray of integers
- 981. Time based key value storage
- 982. A triple with a bitwise and zero
- 987. The vertical traversal of a binary tree
- 992. K Sub array of different integers
- 1001. Grid lighting
- 1002. Find common characters
- 1010. The total duration can be 60 The song of division
- 1015. Can be K The smallest integer that is divisible
- 1027. The longest arithmetic sequence
- 1036. Escape the maze
- 1048. The longest string chain
- 105. Construction of binary trees from traversal sequences of preorder and middle order
- 106. Construct binary tree from middle order and post order traversal sequence
- 1072. Flip by column to get the maximum number of equal rows
- 1074. The sum of the elements is the number of submatrixes of the target value
- 1086. The average score of the top five subjects
- 1090. The maximum value affected by the tag
- 1100. The length is K There is no repetition in the string
- 1122. Relative sorting of arrays
- 1123. The closest common ancestor of the deepest leaf node
- 1124. The longest period of good performance
- 1128. Number of equivalent domino pairs
- 1133. Maximum unique number
- 1138. The path on the letterboard
- 1146. Snapshot array
- 1152. Analysis of user's website visiting behavior
- 1153. String conversion
- 1160. spell the words
- 1165. Single keyboard
- 1166. Designing a file system
- 1169. Query invalid transactions
- 1170. Compare the frequency of the smallest letter in a string
- 1171. Delete consecutive nodes with zero sum from the linked list
- 1172. Plate stack
- 1177. Construct palindrome string detection
- 1178. Guess the riddle
- 1181. Front and back stitching
- 1189. “ balloon ” Maximum number of
- 1198. Find the smallest common element in all rows
- 12. Integer to Roman number
- 1202. Exchange elements in a string
- 1207. Unique occurrences
- 1213. The intersection of three ordered arrays
- 1218. The longest definite difference subsequence
- 1224. Maximum equal frequency
- 1244. To make the best of the rankings
- 1248. Statistics 「 Graceful subarray 」
- 1257. The smallest common area
- 1258. Synonym sentence
- 126. The word chain II
- 1261. Look for elements in the contaminated binary tree
- 127. The word chain
- 1275. Find out the winner of tic tac toe
- 128. The longest continuous sequence
- 1282. User groups
- 1296. Divide an array into a set of consecutive numbers
- 1297. The maximum number of substrings
- 13. Roman numeral to integer
- 1311. Get videos your friends have watched
- 133. Clone map
- 1331. Array number conversion
- 1338. Halve the size of the array
- 1345. Jumping game IV
- 1346. Check the existence of integers and their multiples
- 1347. The minimum number of steps to make heterotopic words
- 1348. Tweet count
- 1357. every other n A discount for one customer
- 1358. The number of substrings containing all three characters
- 1365. How many numbers are smaller than the current number
- 1366. Rank the team by voting
- 1370. Up down string
- 1371. Each vowel contains an even number of times the longest substring
- 138. Copy list with random pointer
- 1386. Seating the cinema
- 139. Word splitting
- 1394. Find the lucky number in the array
- 1396. Design the subway system
- 1399. Count the number of the largest groups
- 140. Word splitting II
- 1400. structure K Palindrome strings
- 141. Circular list
- 1410. HTML Entity Resolver
- 1418. Order display form
- 142. Circular list II
- 1426. Number elements
- 1429. The first number
- 1436. Travel terminal
- 1442. The number of triples that form two exclusive or equal arrays
- 1443. The minimum time to collect all the apples on the tree
- 146. LRU cache
- 1460. Make two arrays equal by flipping the rotor array
- 1461. Check whether a string contains all the length of K The binary substring of
- 1477. Find two non overlapping subarrays whose sum is the target value
- 1481. The minimum number of different integers
- 1485. Clone a binary tree with random pointers
- 1487. Make sure the file name is unique
- 1488. Avoid flooding
- 149. The most points on the line
- 1490. clone N Fork tree
- 1496. Determine whether the paths intersect
- 1497. Check whether array pairs can be k to be divisible by
- 1500. Design document sharing system
- 1506. find N The root node of the fork tree
- 1512. A good number of pairs
- 1519. The number of nodes with the same label in the subtree
- 1540. K Operations change string
- 1542. Find the longest favorite substring
- 1546. The maximum number of non empty subarrays with and as the target value and without overlapping
- 1554. A string with only one different character
- 1570. Dot product of two sparse vectors
- 1577. The square of a number is equal to the method number of the product of two numbers
- 159. The longest substring containing at most two different characters
- 1590. Make arrays and can be P to be divisible by
- 1593. Split the string to maximize the number of unique substrings
- 160. Intersecting list
- 1600. The order of succession to the throne
- 1604. Warn people who use the same employee card more than three times in an hour
- 1624. The longest substring between two identical characters
- 1636. Sort the array in ascending order by frequency
- 1638. Count the number of substrings with only one character difference
- 1640. Can you join to form an array
- 1650. The nearest common ancestor of a binary tree III
- 1656. Design ordered flow
- 1657. Determine whether two strings are close to
- 1658. take x Reduced to 0 Minimum operands of
- 166. Fractions to decimals
- 1660. Correct binary tree
- 1674. The minimum number of operations to make arrays complementary
- 1679. K The maximum number of sum pairs
- 1684. Count the number of consistent strings
- 169. Most elements
- 1695. Delete the maximum score of the subarray
- 17. Letter combination of telephone number
- 170. Sum of two numbers III - Data structure design
- 1711. Big meal count
- 1713. Get the minimum number of operations of subsequence
- 1726. Coproduct tuple
- 1737. The minimum number of characters to be changed to satisfy one of the three conditions
- 1740. Find the distance in the binary tree
- 1742. The maximum number of balls in the box
- 1743. Restore an array from a pair of adjacent elements
- 1748. The sum of the only elements
- 1756. Design recently used （MRU） queue
- 1763. The longest nice substring
- 1772. Rank functions by popularity
- 1775. Make the sum of arrays equal by the least number of operations
- 1781. The sum of all substrings
- 1790. Can performing only one string exchange make two strings equal
- 1794. Count the number of substring pairs with the smallest distance
- 1796. The second largest number in a string
- 1797. Design a verification system
- 1804. Realization Trie （ Prefix tree ） II
- 1805. The number of different integers in a string
- 1807. Replace the parentheses in the string
- 1814. Count the number of good pairs in an array
- 1817. Find user active minutes
- 1832. Judge whether the sentence is a full letter sentence
- 1836. Remove duplicate elements from the unsorted linked list
- 1852. The number of types of numbers in each subarray
- 1857. The maximum color value in a directed graph
- 1865. Find the subscript pair for the specified value
- 187. Repetitive DNA Sequence
- 1876. Substrings of three different characters
- 1893. Check that all integers in the region are overwritten
- 1897. Reassign characters so that all strings are equal
- 1906. The minimum value of the absolute value of the query difference
- 1912. Design movie rental system
- 1915. The number of most beautiful substrings
- 1930. The length is 3 Different palindrome subsequences
- 1932. Merge multiple binary search trees
- 1935. The maximum number of words that can be entered
- 1940. Sort the longest common subsequence between arrays
- 1941. Check that all characters appear the same number of times
- 1948. Delete duplicate folders in the system
- 1993. Operations on the tree
- 2001. Number of groups of interchangeable rectangles
- 2006. The absolute value of the difference is K Number to number
- 2007. Restore the original array from the double array
- 2013. Detection square
- 202. Happy number
- 2025. The maximum number of schemes to split the array
- 2032. Values that appear in at least two arrays
- 2034. Stock prices fluctuate
- 2043. Simple banking system
- 205. Isomorphic Strings
- 2053. No K A unique string
- 2062. Count the vowel substrings in the string
- 2068. Check that the two strings are almost equal
- 208. Realization Trie ( Prefix tree )
- 2080. The frequency of querying numbers in the interval
- 2083. Find the total number of substrings beginning and ending with the same letter
- 2085. Count the public strings that appear once
- 2094. find 3 Bit even
- 2099. Find and the maximum length is K The subsequence
- 2103. Ring and rod
- 2107. Share K The number of unique flavors after a candy
- 2115. Find all the dishes you can make from a given raw material
- 2121. The sum of the intervals of the same elements
- 2122. Restore the original array
- 2131. The longest palindrome string obtained by connecting two letter words
- 2133. Check whether each row and column contains all integers
- 2135. Count the number of words you can get by adding letters
- 2150. Find all the numbers in the array
- 2152. The minimum number of lines required to pass through all points
- 2154. Multiply the found value by 2
- 2166. Design bit set
- 2168. The number of unique substrings with the same frequency for each number
- 217. There are duplicate elements
- 2170. The minimum number of operands to make an array an alternating array
- 2186. The minimum number of steps to make two strings into alphabetic ectopic words
- 219. There are duplicate elements II
- 2190. Immediately following in the array key Then the most frequent number
- 2196. Create a binary tree according to the description
- 2201. Statistics of the artifacts that can be extracted
- 2206. Divide the array into equal pairs
- 2215. Find out the difference between the two arrays
- 2225. Find the player who lost zero or one game
- 2227. Encrypt and decrypt strings
- 2244. The minimum number of rounds required to complete all tasks

# 914. Card groups

# 904. Fruit baskets

# 781. Rabbits in the forest

```
class Solution:
def numRabbits(self, answers: List[int]) -> int:
n, ans = len(answers), 0
cnt = Counter(answers)
for k, v in cnt.items():
ans += (v + k) // (k + 1) * (k + 1)
#ans += ceil(v/(k+1)) * (k + 1)
return ans
```

```
class Solution {
public int numRabbits(int[] answers) {
int ans = 0;
Map<Integer, Integer> map = new HashMap<>();
for (int x : answers)
map.put(x, map.getOrDefault(x, 0) + 1);
for (Map.Entry<Integer, Integer> entry : map.entrySet()) {
int k = entry.getKey(), v = entry.getValue();
ans += (k + v) / (k + 1) * (k + 1);
}
return ans;
}
}
```

# Basic knowledge of

### The first 32 course

- 1897. Reassign characters so that all strings are equal
- Basic knowledge of
- 1331. Array number conversion
- 1002. Find common characters
- Basic knowledge of
- 914. Card groups
- 904. Fruit baskets
- [781. Rabbits in the forest ](https://leetcode-cn.com/problems/rabbits-in-forest/)
- Basic knowledge of
- [648. Word substitution ](https://leetcode-cn.com/problems/replace-words/)
- 389. Make a difference
- *1700. Number of students unable to have lunch
- Basic knowledge of
- 229. Find mode II
- 1365. How many numbers are smaller than the current number
- 888. Fair candy exchange
- 1452. Collection list
- Basic knowledge of
- 383. Ransom letter
- 997. Find the judge in town
- 229. Find mode II
- 575. Divide candy
- [1054. Bar codes with equal distances ](https://leetcode-cn.com/problems/distant-barcodes/)
- 560. And for K Subarray
- [41. First positive number missing ](https://leetcode-cn.com/problems/first-missing-positive/)
- 242. Effective alphabetic words
- 244. The shortest word distance II
- 246. Centrosymmetric number
- 249. Shift string grouping
- 264. Ugly number II
- 266. Palindrome arrangement
- 267. Palindrome arrangement II
- 268. Missing numbers
- 76. Minimum cover substring
- 288. The only abbreviation of a word
- [290. Rules of words ](https://leetcode-cn.com/problems/word-pattern/)
- 291. Rules of words II
- 299. Guess the number game
- 3. Longest substring without repeating characters
- 30. Concatenate the substrings of all words
- 311. Multiplication of sparse matrices
- 313. Super ugly number
- 314. Vertical traversal of binary trees
- 325. And equal to k The longest subarray length of
- 336. The palindrome is right
- 340. At most K Longest substring of different characters
- 347. front K High frequency elements
- 348. Design tic tac toe chess
- 349. Intersection of two arrays
- 350. Intersection of two arrays II
- 355. Design twitter
- 356. Line mirror image
- 358. K The distance interval rearranges the string
- 359. Log rate limiter
- 36. Effective Sudoku
- 362. Hit the counter
- 379. Telephone directory management system
- 380. O(1) Time insertion 、 Delete and get random elements
- 381. O(1) Time insertion 、 Delete and get random elements - Allow repetition
- 387. The first unique character in the string
- 395. There are at least K The longest substring of repeated characters
- 398. Random number index
- 409. Longest palindrome
- 421. The maximum exclusive or value of two numbers in an array
- 423. Reconstructing Chinese from English
- 424. The longest repeated character after replacement
- 432. whole O(1) Data structure of
- 433. Minimal genetic change
- 438. Find all alphabetic words in the string
- 442. Duplicate data in array
- 447. The number of boomerangs
- 448. Find all the missing numbers in the array
- 451. Sort the characters according to their frequency of occurrence
- 454. Add four numbers II
- 457. Whether there is a loop in the ring array
- 460. LFU cache
- 480. Sliding window median
- 49. Letter heterotopic word grouping
- 491. Increasing subsequence
- 496. Next bigger element I
- 500. Keyboard line
- 508. The most frequent sub tree elements and
- 519. Random flip matrix
- 522. The longest special sequence II
- 523. Continuous subarrays and
- 531. Lonely pixels I
- 532. Array k-diff Number pair
- 533. Lonely pixels II
- 535. TinyURL Encryption and decryption
- 567. Arrangement of strings
- 582. Kill the process
- 588. Design memory file system
- 594. The longest harmonious subsequence
- 599. The minimum index sum of two lists
- 604. Iteratively compress strings
- 609. Find duplicate files in the system
- 616. Add bold tags to strings
- 621. Task scheduler
- 632. Minimum range
- 635. Design the log storage system
- 645. The wrong set
- 652. Look for duplicate subtrees
- 653. Sum of two numbers IV - Input BST
- 659. Split the array into successive subsequences
- 676. Implement a magic dictionary
- 677. Key value mapping
- 690. The importance of employees
- 692. front K High frequency words
- 694. The number of different islands
- 697. The degree of the array
- 705. Design hash sets
- 706. Design hash map
- 710. Random numbers in the blacklist
- 711. The number of different islands II
- 720. The longest word in the dictionary
- 726. The number of atoms
- 73. Matrix zeroing
- 734. Sentence similarity
- 736. Lisp Syntax parsing
- 737. Sentence similarity II
- 740. Delete and get points
- 748. The shortest complement
- 752. Open the turntable lock
- 758. Bold words in strings
- 760. Find the displacement map
- 763. Division of alphabet
- 767. Refactoring strings
- 770. Basic calculator IV
- 771. Gems and stones
- 791. Custom string sorting
- 792. Number of words to match subsequence
- 804. The only Morse code word
- 811. Subdomain access count
- 815. Bus routes
- 817. Linked list component
- 819. The most common word
- 820. Compression coding of words
- 822. Flip card game
- 823. Binary trees with factors
- 859. Intimate string
- 865. The smallest subtree with all the deepest nodes
- 868. Binary spacing
- 873. The length of the longest Fibonacci subsequence
- 884. Unusual words in two sentences
- 889. Construct binary tree according to preorder and postorder traversal
- 890. Find and replace patterns
- 893. Special equivalent string group
- 895. Maximum frequency stack
- 911. Online elections
- 916. Word subsets
- 923. Many possibilities of the sum of three
- 929. Unique email address
- 930. And the same binary subarray
- 939. Minimum area rectangle
- 953. Verification of an alien language dictionary
- 954. Double pair array
- 957. N After the day of
- 961. In length 2N Find duplicates in the array of N Secondary elements
- 966. Vowel spelling checker
- 970. Strong integer
- 974. And can be K A subarray of integers
- 981. Time based key value storage
- 982. A triple with a bitwise and zero
- 987. The vertical traversal of a binary tree
- 992. K Sub array of different integers
- 1001. Grid lighting
- 1002. Find common characters
- 1010. The total duration can be 60 The song of division
- 1015. Can be K The smallest integer that is divisible
- 1027. The longest arithmetic sequence
- 1036. Escape the maze
- 1048. The longest string chain
- 105. Construction of binary trees from traversal sequences of preorder and middle order
- 106. Construct binary tree from middle order and post order traversal sequence
- 1072. Flip by column to get the maximum number of equal rows
- 1074. The sum of the elements is the number of submatrixes of the target value
- 1086. The average score of the top five subjects
- 1090. The maximum value affected by the tag
- 1100. The length is K There is no repetition in the string
- 1122. Relative sorting of arrays
- 1123. The closest common ancestor of the deepest leaf node
- 1124. The longest period of good performance
- 1128. Number of equivalent domino pairs
- 1133. Maximum unique number
- 1138. The path on the letterboard
- 1146. Snapshot array
- 1152. Analysis of user's website visiting behavior
- 1153. String conversion
- 1160. spell the words
- 1165. Single keyboard
- 1166. Designing a file system
- 1169. Query invalid transactions
- 1170. Compare the frequency of the smallest letter in a string
- 1171. Delete consecutive nodes with zero sum from the linked list
- 1172. Plate stack
- 1177. Construct palindrome string detection
- 1178. Guess the riddle
- 1181. Front and back stitching
- 1189. “ balloon ” Maximum number of
- 1198. Find the smallest common element in all rows
- 12. Integer to Roman number
- 1202. Exchange elements in a string
- 1207. Unique occurrences
- 1213. The intersection of three ordered arrays
- 1218. The longest definite difference subsequence
- 1224. Maximum equal frequency
- 1244. To make the best of the rankings
- 1248. Statistics 「 Graceful subarray 」
- 1257. The smallest common area
- 1258. Synonym sentence
- 126. The word chain II
- 1261. Look for elements in the contaminated binary tree
- 127. The word chain
- 1275. Find out the winner of tic tac toe
- 128. The longest continuous sequence
- 1282. User groups
- 1296. Divide an array into a set of consecutive numbers
- 1297. The maximum number of substrings
- 13. Roman numeral to integer
- 1311. Get videos your friends have watched
- 133. Clone map
- 1331. Array number conversion
- 1338. Halve the size of the array
- 1345. Jumping game IV
- 1346. Check the existence of integers and their multiples
- 1347. The minimum number of steps to make heterotopic words
- 1348. Tweet count
- 1357. every other n A discount for one customer
- 1358. The number of substrings containing all three characters
- 1365. How many numbers are smaller than the current number
- 1366. Rank the team by voting
- 1370. Up down string
- 1371. Each vowel contains an even number of times the longest substring
- 138. Copy list with random pointer
- 1386. Seating the cinema
- 139. Word splitting
- 1394. Find the lucky number in the array
- 1396. Design the subway system
- 1399. Count the number of the largest groups
- 140. Word splitting II
- 1400. structure K Palindrome strings
- 141. Circular list
- 1410. HTML Entity Resolver
- 1418. Order display form
- 142. Circular list II
- 1426. Number elements
- 1429. The first number
- 1436. Travel terminal
- 1442. The number of triples that form two exclusive or equal arrays
- 1443. The minimum time to collect all the apples on the tree
- 146. LRU cache
- 1460. Make two arrays equal by flipping the rotor array
- 1461. Check whether a string contains all the length of K The binary substring of
- 1477. Find two non overlapping subarrays whose sum is the target value
- 1481. The minimum number of different integers
- 1485. Clone a binary tree with random pointers
- 1487. Make sure the file name is unique
- 1488. Avoid flooding
- 149. The most points on the line
- 1490. clone N Fork tree
- 1496. Determine whether the paths intersect
- 1497. Check whether array pairs can be k to be divisible by
- 1500. Design document sharing system
- 1506. find N The root node of the fork tree
- 1512. A good number of pairs
- 1519. The number of nodes with the same label in the subtree
- 1540. K Operations change string
- 1542. Find the longest favorite substring
- 1546. The maximum number of non empty subarrays with and as the target value and without overlapping
- 1554. A string with only one different character
- 1570. Dot product of two sparse vectors
- 1577. The square of a number is equal to the method number of the product of two numbers
- 159. The longest substring containing at most two different characters
- 1590. Make arrays and can be P to be divisible by
- 1593. Split the string to maximize the number of unique substrings
- 160. Intersecting list
- 1600. The order of succession to the throne
- 1604. Warn people who use the same employee card more than three times in an hour
- 1624. The longest substring between two identical characters
- 1636. Sort the array in ascending order by frequency
- 1638. Count the number of substrings with only one character difference
- 1640. Can you join to form an array
- 1650. The nearest common ancestor of a binary tree III
- 1656. Design ordered flow
- 1657. Determine whether two strings are close to
- 1658. take x Reduced to 0 Minimum operands of
- 166. Fractions to decimals
- 1660. Correct binary tree
- 1674. The minimum number of operations to make arrays complementary
- 1679. K The maximum number of sum pairs
- 1684. Count the number of consistent strings
- 169. Most elements
- 1695. Delete the maximum score of the subarray
- 17. Letter combination of telephone number
- 170. Sum of two numbers III - Data structure design
- 1711. Big meal count
- 1713. Get the minimum number of operations of subsequence
- 1726. Coproduct tuple
- 1737. The minimum number of characters to be changed to satisfy one of the three conditions
- 1740. Find the distance in the binary tree
- 1742. The maximum number of balls in the box
- 1743. Restore an array from a pair of adjacent elements
- 1748. The sum of the only elements
- 1756. Design recently used （MRU） queue
- 1763. The longest nice substring
- 1772. Rank functions by popularity
- 1775. Make the sum of arrays equal by the least number of operations
- 1781. The sum of all substrings
- 1790. Can performing only one string exchange make two strings equal
- 1794. Count the number of substring pairs with the smallest distance
- 1796. The second largest number in a string
- 1797. Design a verification system
- 1804. Realization Trie （ Prefix tree ） II
- 1805. The number of different integers in a string
- 1807. Replace the parentheses in the string
- 1814. Count the number of good pairs in an array
- 1817. Find user active minutes
- 1832. Judge whether the sentence is a full letter sentence
- 1836. Remove duplicate elements from the unsorted linked list
- 1852. The number of types of numbers in each subarray
- 1857. The maximum color value in a directed graph
- 1865. Find the subscript pair for the specified value
- 187. Repetitive DNA Sequence
- 1876. Substrings of three different characters
- 1893. Check that all integers in the region are overwritten
- 1897. Reassign characters so that all strings are equal
- 1906. The minimum value of the absolute value of the query difference
- 1912. Design movie rental system
- 1915. The number of most beautiful substrings
- 1930. The length is 3 Different palindrome subsequences
- 1932. Merge multiple binary search trees
- 1935. The maximum number of words that can be entered
- 1940. Sort the longest common subsequence between arrays
- 1941. Check that all characters appear the same number of times
- 1948. Delete duplicate folders in the system
- 1993. Operations on the tree
- 2001. Number of groups of interchangeable rectangles
- 2006. The absolute value of the difference is K Number to number
- 2007. Restore the original array from the double array
- 2013. Detection square
- 202. Happy number
- 2025. The maximum number of schemes to split the array
- 2032. Values that appear in at least two arrays
- 2034. Stock prices fluctuate
- 2043. Simple banking system
- 205. Isomorphic Strings
- 2053. No K A unique string
- 2062. Count the vowel substrings in the string
- 2068. Check that the two strings are almost equal
- 208. Realization Trie ( Prefix tree )
- 2080. The frequency of querying numbers in the interval
- 2083. Find the total number of substrings beginning and ending with the same letter
- 2085. Count the public strings that appear once
- 2094. find 3 Bit even
- 2099. Find and the maximum length is K The subsequence
- 2103. Ring and rod
- 2107. Share K The number of unique flavors after a candy
- 2115. Find all the dishes you can make from a given raw material
- 2121. The sum of the intervals of the same elements
- 2122. Restore the original array
- 2131. The longest palindrome string obtained by connecting two letter words
- 2133. Check whether each row and column contains all integers
- 2135. Count the number of words you can get by adding letters
- 2150. Find all the numbers in the array
- 2152. The minimum number of lines required to pass through all points
- 2154. Multiply the found value by 2
- 2166. Design bit set
- 2168. The number of unique substrings with the same frequency for each number
- 217. There are duplicate elements
- 2170. The minimum number of operands to make an array an alternating array
- 2186. The minimum number of steps to make two strings into alphabetic ectopic words
- 219. There are duplicate elements II
- 2190. Immediately following in the array key Then the most frequent number
- 2196. Create a binary tree according to the description
- 2201. Statistics of the artifacts that can be extracted
- 2206. Divide the array into equal pairs
- 2215. Find out the difference between the two arrays
- 2225. Find the player who lost zero or one game
- 2227. Encrypt and decrypt strings
- 2244. The minimum number of rounds required to complete all tasks

# 648. Word substitution

```
class Solution:
def replaceWords(self, dictionary: List[str], sentence: str) -> str:
word = sentence.split()
d = set(dictionary)
ans = []
for w in word:
for i in range(len(w)):
s = w[:i+1]
if s in d:
ans.append(w[:i+1])
break
else: ans.append(w)
return ' '.join(ans)
```

```
class Solution {
public String replaceWords(List<String> dictionary, String sentence) {
String[] t = sentence.split(" ");
List<String> ans = new ArrayList<>();
Set<String> d = new HashSet(dictionary);
sign:
for (String w : t){
for (int i = 0; i < w.length(); i++){
String x = w.substring(0, i+1);
if (d.contains(x)){
ans.add(x);
continue sign;
}
}
ans.add(w);
}
String s = String.join(" ", ans);
return s;
}
}
```

# 389. Make a difference

# *1700. Number of students unable to have lunch

# Basic knowledge of

### The first 33 course

- 1897. Reassign characters so that all strings are equal
- Basic knowledge of
- 1331. Array number conversion
- 1002. Find common characters
- Basic knowledge of
- 914. Card groups
- 904. Fruit baskets
- [781. Rabbits in the forest ](https://leetcode-cn.com/problems/rabbits-in-forest/)
- Basic knowledge of
- [648. Word substitution ](https://leetcode-cn.com/problems/replace-words/)
- 389. Make a difference
- *1700. Number of students unable to have lunch
- Basic knowledge of
- 229. Find mode II
- 1365. How many numbers are smaller than the current number
- 888. Fair candy exchange
- 1452. Collection list
- Basic knowledge of
- 383. Ransom letter
- 997. Find the judge in town
- 229. Find mode II
- 575. Divide candy
- [1054. Bar codes with equal distances ](https://leetcode-cn.com/problems/distant-barcodes/)
- 560. And for K Subarray
- [41. First positive number missing ](https://leetcode-cn.com/problems/first-missing-positive/)
- 242. Effective alphabetic words
- 244. The shortest word distance II
- 246. Centrosymmetric number
- 249. Shift string grouping
- 264. Ugly number II
- 266. Palindrome arrangement
- 267. Palindrome arrangement II
- 268. Missing numbers
- 76. Minimum cover substring
- 288. The only abbreviation of a word
- [290. Rules of words ](https://leetcode-cn.com/problems/word-pattern/)
- 291. Rules of words II
- 299. Guess the number game
- 3. Longest substring without repeating characters
- 30. Concatenate the substrings of all words
- 311. Multiplication of sparse matrices
- 313. Super ugly number
- 314. Vertical traversal of binary trees
- 325. And equal to k The longest subarray length of
- 336. The palindrome is right
- 340. At most K Longest substring of different characters
- 347. front K High frequency elements
- 348. Design tic tac toe chess
- 349. Intersection of two arrays
- 350. Intersection of two arrays II
- 355. Design twitter
- 356. Line mirror image
- 358. K The distance interval rearranges the string
- 359. Log rate limiter
- 36. Effective Sudoku
- 362. Hit the counter
- 379. Telephone directory management system
- 380. O(1) Time insertion 、 Delete and get random elements
- 381. O(1) Time insertion 、 Delete and get random elements - Allow repetition
- 387. The first unique character in the string
- 395. There are at least K The longest substring of repeated characters
- 398. Random number index
- 409. Longest palindrome
- 421. The maximum exclusive or value of two numbers in an array
- 423. Reconstructing Chinese from English
- 424. The longest repeated character after replacement
- 432. whole O(1) Data structure of
- 433. Minimal genetic change
- 438. Find all alphabetic words in the string
- 442. Duplicate data in array
- 447. The number of boomerangs
- 448. Find all the missing numbers in the array
- 451. Sort the characters according to their frequency of occurrence
- 454. Add four numbers II
- 457. Whether there is a loop in the ring array
- 460. LFU cache
- 480. Sliding window median
- 49. Letter heterotopic word grouping
- 491. Increasing subsequence
- 496. Next bigger element I
- 500. Keyboard line
- 508. The most frequent sub tree elements and
- 519. Random flip matrix
- 522. The longest special sequence II
- 523. Continuous subarrays and
- 531. Lonely pixels I
- 532. Array k-diff Number pair
- 533. Lonely pixels II
- 535. TinyURL Encryption and decryption
- 567. Arrangement of strings
- 582. Kill the process
- 588. Design memory file system
- 594. The longest harmonious subsequence
- 599. The minimum index sum of two lists
- 604. Iteratively compress strings
- 609. Find duplicate files in the system
- 616. Add bold tags to strings
- 621. Task scheduler
- 632. Minimum range
- 635. Design the log storage system
- 645. The wrong set
- 652. Look for duplicate subtrees
- 653. Sum of two numbers IV - Input BST
- 659. Split the array into successive subsequences
- 676. Implement a magic dictionary
- 677. Key value mapping
- 690. The importance of employees
- 692. front K High frequency words
- 694. The number of different islands
- 697. The degree of the array
- 705. Design hash sets
- 706. Design hash map
- 710. Random numbers in the blacklist
- 711. The number of different islands II
- 720. The longest word in the dictionary
- 726. The number of atoms
- 73. Matrix zeroing
- 734. Sentence similarity
- 736. Lisp Syntax parsing
- 737. Sentence similarity II
- 740. Delete and get points
- 748. The shortest complement
- 752. Open the turntable lock
- 758. Bold words in strings
- 760. Find the displacement map
- 763. Division of alphabet
- 767. Refactoring strings
- 770. Basic calculator IV
- 771. Gems and stones
- 791. Custom string sorting
- 792. Number of words to match subsequence
- 804. The only Morse code word
- 811. Subdomain access count
- 815. Bus routes
- 817. Linked list component
- 819. The most common word
- 820. Compression coding of words
- 822. Flip card game
- 823. Binary trees with factors
- 859. Intimate string
- 865. The smallest subtree with all the deepest nodes
- 868. Binary spacing
- 873. The length of the longest Fibonacci subsequence
- 884. Unusual words in two sentences
- 889. Construct binary tree according to preorder and postorder traversal
- 890. Find and replace patterns
- 893. Special equivalent string group
- 895. Maximum frequency stack
- 911. Online elections
- 916. Word subsets
- 923. Many possibilities of the sum of three
- 929. Unique email address
- 930. And the same binary subarray
- 939. Minimum area rectangle
- 953. Verification of an alien language dictionary
- 954. Double pair array
- 957. N After the day of
- 961. In length 2N Find duplicates in the array of N Secondary elements
- 966. Vowel spelling checker
- 970. Strong integer
- 974. And can be K A subarray of integers
- 981. Time based key value storage
- 982. A triple with a bitwise and zero
- 987. The vertical traversal of a binary tree
- 992. K Sub array of different integers
- 1001. Grid lighting
- 1002. Find common characters
- 1010. The total duration can be 60 The song of division
- 1015. Can be K The smallest integer that is divisible
- 1027. The longest arithmetic sequence
- 1036. Escape the maze
- 1048. The longest string chain
- 105. Construction of binary trees from traversal sequences of preorder and middle order
- 106. Construct binary tree from middle order and post order traversal sequence
- 1072. Flip by column to get the maximum number of equal rows
- 1074. The sum of the elements is the number of submatrixes of the target value
- 1086. The average score of the top five subjects
- 1090. The maximum value affected by the tag
- 1100. The length is K There is no repetition in the string
- 1122. Relative sorting of arrays
- 1123. The closest common ancestor of the deepest leaf node
- 1124. The longest period of good performance
- 1128. Number of equivalent domino pairs
- 1133. Maximum unique number
- 1138. The path on the letterboard
- 1146. Snapshot array
- 1152. Analysis of user's website visiting behavior
- 1153. String conversion
- 1160. spell the words
- 1165. Single keyboard
- 1166. Designing a file system
- 1169. Query invalid transactions
- 1170. Compare the frequency of the smallest letter in a string
- 1171. Delete consecutive nodes with zero sum from the linked list
- 1172. Plate stack
- 1177. Construct palindrome string detection
- 1178. Guess the riddle
- 1181. Front and back stitching
- 1189. “ balloon ” Maximum number of
- 1198. Find the smallest common element in all rows
- 12. Integer to Roman number
- 1202. Exchange elements in a string
- 1207. Unique occurrences
- 1213. The intersection of three ordered arrays
- 1218. The longest definite difference subsequence
- 1224. Maximum equal frequency
- 1244. To make the best of the rankings
- 1248. Statistics 「 Graceful subarray 」
- 1257. The smallest common area
- 1258. Synonym sentence
- 126. The word chain II
- 1261. Look for elements in the contaminated binary tree
- 127. The word chain
- 1275. Find out the winner of tic tac toe
- 128. The longest continuous sequence
- 1282. User groups
- 1296. Divide an array into a set of consecutive numbers
- 1297. The maximum number of substrings
- 13. Roman numeral to integer
- 1311. Get videos your friends have watched
- 133. Clone map
- 1331. Array number conversion
- 1338. Halve the size of the array
- 1345. Jumping game IV
- 1346. Check the existence of integers and their multiples
- 1347. The minimum number of steps to make heterotopic words
- 1348. Tweet count
- 1357. every other n A discount for one customer
- 1358. The number of substrings containing all three characters
- 1365. How many numbers are smaller than the current number
- 1366. Rank the team by voting
- 1370. Up down string
- 1371. Each vowel contains an even number of times the longest substring
- 138. Copy list with random pointer
- 1386. Seating the cinema
- 139. Word splitting
- 1394. Find the lucky number in the array
- 1396. Design the subway system
- 1399. Count the number of the largest groups
- 140. Word splitting II
- 1400. structure K Palindrome strings
- 141. Circular list
- 1410. HTML Entity Resolver
- 1418. Order display form
- 142. Circular list II
- 1426. Number elements
- 1429. The first number
- 1436. Travel terminal
- 1442. The number of triples that form two exclusive or equal arrays
- 1443. The minimum time to collect all the apples on the tree
- 146. LRU cache
- 1460. Make two arrays equal by flipping the rotor array
- 1461. Check whether a string contains all the length of K The binary substring of
- 1477. Find two non overlapping subarrays whose sum is the target value
- 1481. The minimum number of different integers
- 1485. Clone a binary tree with random pointers
- 1487. Make sure the file name is unique
- 1488. Avoid flooding
- 149. The most points on the line
- 1490. clone N Fork tree
- 1496. Determine whether the paths intersect
- 1497. Check whether array pairs can be k to be divisible by
- 1500. Design document sharing system
- 1506. find N The root node of the fork tree
- 1512. A good number of pairs
- 1519. The number of nodes with the same label in the subtree
- 1540. K Operations change string
- 1542. Find the longest favorite substring
- 1546. The maximum number of non empty subarrays with and as the target value and without overlapping
- 1554. A string with only one different character
- 1570. Dot product of two sparse vectors
- 1577. The square of a number is equal to the method number of the product of two numbers
- 159. The longest substring containing at most two different characters
- 1590. Make arrays and can be P to be divisible by
- 1593. Split the string to maximize the number of unique substrings
- 160. Intersecting list
- 1600. The order of succession to the throne
- 1604. Warn people who use the same employee card more than three times in an hour
- 1624. The longest substring between two identical characters
- 1636. Sort the array in ascending order by frequency
- 1638. Count the number of substrings with only one character difference
- 1640. Can you join to form an array
- 1650. The nearest common ancestor of a binary tree III
- 1656. Design ordered flow
- 1657. Determine whether two strings are close to
- 1658. take x Reduced to 0 Minimum operands of
- 166. Fractions to decimals
- 1660. Correct binary tree
- 1674. The minimum number of operations to make arrays complementary
- 1679. K The maximum number of sum pairs
- 1684. Count the number of consistent strings
- 169. Most elements
- 1695. Delete the maximum score of the subarray
- 17. Letter combination of telephone number
- 170. Sum of two numbers III - Data structure design
- 1711. Big meal count
- 1713. Get the minimum number of operations of subsequence
- 1726. Coproduct tuple
- 1737. The minimum number of characters to be changed to satisfy one of the three conditions
- 1740. Find the distance in the binary tree
- 1742. The maximum number of balls in the box
- 1743. Restore an array from a pair of adjacent elements
- 1748. The sum of the only elements
- 1756. Design recently used （MRU） queue
- 1763. The longest nice substring
- 1772. Rank functions by popularity
- 1775. Make the sum of arrays equal by the least number of operations
- 1781. The sum of all substrings
- 1790. Can performing only one string exchange make two strings equal
- 1794. Count the number of substring pairs with the smallest distance
- 1796. The second largest number in a string
- 1797. Design a verification system
- 1804. Realization Trie （ Prefix tree ） II
- 1805. The number of different integers in a string
- 1807. Replace the parentheses in the string
- 1814. Count the number of good pairs in an array
- 1817. Find user active minutes
- 1832. Judge whether the sentence is a full letter sentence
- 1836. Remove duplicate elements from the unsorted linked list
- 1852. The number of types of numbers in each subarray
- 1857. The maximum color value in a directed graph
- 1865. Find the subscript pair for the specified value
- 187. Repetitive DNA Sequence
- 1876. Substrings of three different characters
- 1893. Check that all integers in the region are overwritten
- 1897. Reassign characters so that all strings are equal
- 1906. The minimum value of the absolute value of the query difference
- 1912. Design movie rental system
- 1915. The number of most beautiful substrings
- 1930. The length is 3 Different palindrome subsequences
- 1932. Merge multiple binary search trees
- 1935. The maximum number of words that can be entered
- 1940. Sort the longest common subsequence between arrays
- 1941. Check that all characters appear the same number of times
- 1948. Delete duplicate folders in the system
- 1993. Operations on the tree
- 2001. Number of groups of interchangeable rectangles
- 2006. The absolute value of the difference is K Number to number
- 2007. Restore the original array from the double array
- 2013. Detection square
- 202. Happy number
- 2025. The maximum number of schemes to split the array
- 2032. Values that appear in at least two arrays
- 2034. Stock prices fluctuate
- 2043. Simple banking system
- 205. Isomorphic Strings
- 2053. No K A unique string
- 2062. Count the vowel substrings in the string
- 2068. Check that the two strings are almost equal
- 208. Realization Trie ( Prefix tree )
- 2080. The frequency of querying numbers in the interval
- 2083. Find the total number of substrings beginning and ending with the same letter
- 2085. Count the public strings that appear once
- 2094. find 3 Bit even
- 2099. Find and the maximum length is K The subsequence
- 2103. Ring and rod
- 2107. Share K The number of unique flavors after a candy
- 2115. Find all the dishes you can make from a given raw material
- 2121. The sum of the intervals of the same elements
- 2122. Restore the original array
- 2131. The longest palindrome string obtained by connecting two letter words
- 2133. Check whether each row and column contains all integers
- 2135. Count the number of words you can get by adding letters
- 2150. Find all the numbers in the array
- 2152. The minimum number of lines required to pass through all points
- 2154. Multiply the found value by 2
- 2166. Design bit set
- 2168. The number of unique substrings with the same frequency for each number
- 217. There are duplicate elements
- 2170. The minimum number of operands to make an array an alternating array
- 2186. The minimum number of steps to make two strings into alphabetic ectopic words
- 219. There are duplicate elements II
- 2190. Immediately following in the array key Then the most frequent number
- 2196. Create a binary tree according to the description
- 2201. Statistics of the artifacts that can be extracted
- 2206. Divide the array into equal pairs
- 2215. Find out the difference between the two arrays
- 2225. Find the player who lost zero or one game
- 2227. Encrypt and decrypt strings
- 2244. The minimum number of rounds required to complete all tasks

# 229. Find mode II

# 1365. How many numbers are smaller than the current number

# 888. Fair candy exchange

# 1452. Collection list

# Basic knowledge of

### The first 34 course

- 1897. Reassign characters so that all strings are equal
- Basic knowledge of
- 1331. Array number conversion
- 1002. Find common characters
- Basic knowledge of
- 914. Card groups
- 904. Fruit baskets
- [781. Rabbits in the forest ](https://leetcode-cn.com/problems/rabbits-in-forest/)
- Basic knowledge of
- [648. Word substitution ](https://leetcode-cn.com/problems/replace-words/)
- 389. Make a difference
- *1700. Number of students unable to have lunch
- Basic knowledge of
- 229. Find mode II
- 1365. How many numbers are smaller than the current number
- 888. Fair candy exchange
- 1452. Collection list
- Basic knowledge of
- 383. Ransom letter
- 997. Find the judge in town
- 229. Find mode II
- 575. Divide candy
- [1054. Bar codes with equal distances ](https://leetcode-cn.com/problems/distant-barcodes/)
- 560. And for K Subarray
- [41. First positive number missing ](https://leetcode-cn.com/problems/first-missing-positive/)
- 242. Effective alphabetic words
- 244. The shortest word distance II
- 246. Centrosymmetric number
- 249. Shift string grouping
- 264. Ugly number II
- 266. Palindrome arrangement
- 267. Palindrome arrangement II
- 268. Missing numbers
- 76. Minimum cover substring
- 288. The only abbreviation of a word
- [290. Rules of words ](https://leetcode-cn.com/problems/word-pattern/)
- 291. Rules of words II
- 299. Guess the number game
- 3. Longest substring without repeating characters
- 30. Concatenate the substrings of all words
- 311. Multiplication of sparse matrices
- 313. Super ugly number
- 314. Vertical traversal of binary trees
- 325. And equal to k The longest subarray length of
- 336. The palindrome is right
- 340. At most K Longest substring of different characters
- 347. front K High frequency elements
- 348. Design tic tac toe chess
- 349. Intersection of two arrays
- 350. Intersection of two arrays II
- 355. Design twitter
- 356. Line mirror image
- 358. K The distance interval rearranges the string
- 359. Log rate limiter
- 36. Effective Sudoku
- 362. Hit the counter
- 379. Telephone directory management system
- 380. O(1) Time insertion 、 Delete and get random elements
- 381. O(1) Time insertion 、 Delete and get random elements - Allow repetition
- 387. The first unique character in the string
- 395. There are at least K The longest substring of repeated characters
- 398. Random number index
- 409. Longest palindrome
- 421. The maximum exclusive or value of two numbers in an array
- 423. Reconstructing Chinese from English
- 424. The longest repeated character after replacement
- 432. whole O(1) Data structure of
- 433. Minimal genetic change
- 438. Find all alphabetic words in the string
- 442. Duplicate data in array
- 447. The number of boomerangs
- 448. Find all the missing numbers in the array
- 451. Sort the characters according to their frequency of occurrence
- 454. Add four numbers II
- 457. Whether there is a loop in the ring array
- 460. LFU cache
- 480. Sliding window median
- 49. Letter heterotopic word grouping
- 491. Increasing subsequence
- 496. Next bigger element I
- 500. Keyboard line
- 508. The most frequent sub tree elements and
- 519. Random flip matrix
- 522. The longest special sequence II
- 523. Continuous subarrays and
- 531. Lonely pixels I
- 532. Array k-diff Number pair
- 533. Lonely pixels II
- 535. TinyURL Encryption and decryption
- 567. Arrangement of strings
- 582. Kill the process
- 588. Design memory file system
- 594. The longest harmonious subsequence
- 599. The minimum index sum of two lists
- 604. Iteratively compress strings
- 609. Find duplicate files in the system
- 616. Add bold tags to strings
- 621. Task scheduler
- 632. Minimum range
- 635. Design the log storage system
- 645. The wrong set
- 652. Look for duplicate subtrees
- 653. Sum of two numbers IV - Input BST
- 659. Split the array into successive subsequences
- 676. Implement a magic dictionary
- 677. Key value mapping
- 690. The importance of employees
- 692. front K High frequency words
- 694. The number of different islands
- 697. The degree of the array
- 705. Design hash sets
- 706. Design hash map
- 710. Random numbers in the blacklist
- 711. The number of different islands II
- 720. The longest word in the dictionary
- 726. The number of atoms
- 73. Matrix zeroing
- 734. Sentence similarity
- 736. Lisp Syntax parsing
- 737. Sentence similarity II
- 740. Delete and get points
- 748. The shortest complement
- 752. Open the turntable lock
- 758. Bold words in strings
- 760. Find the displacement map
- 763. Division of alphabet
- 767. Refactoring strings
- 770. Basic calculator IV
- 771. Gems and stones
- 791. Custom string sorting
- 792. Number of words to match subsequence
- 804. The only Morse code word
- 811. Subdomain access count
- 815. Bus routes
- 817. Linked list component
- 819. The most common word
- 820. Compression coding of words
- 822. Flip card game
- 823. Binary trees with factors
- 859. Intimate string
- 865. The smallest subtree with all the deepest nodes
- 868. Binary spacing
- 873. The length of the longest Fibonacci subsequence
- 884. Unusual words in two sentences
- 889. Construct binary tree according to preorder and postorder traversal
- 890. Find and replace patterns
- 893. Special equivalent string group
- 895. Maximum frequency stack
- 911. Online elections
- 916. Word subsets
- 923. Many possibilities of the sum of three
- 929. Unique email address
- 930. And the same binary subarray
- 939. Minimum area rectangle
- 953. Verification of an alien language dictionary
- 954. Double pair array
- 957. N After the day of
- 961. In length 2N Find duplicates in the array of N Secondary elements
- 966. Vowel spelling checker
- 970. Strong integer
- 974. And can be K A subarray of integers
- 981. Time based key value storage
- 982. A triple with a bitwise and zero
- 987. The vertical traversal of a binary tree
- 992. K Sub array of different integers
- 1001. Grid lighting
- 1002. Find common characters
- 1010. The total duration can be 60 The song of division
- 1015. Can be K The smallest integer that is divisible
- 1027. The longest arithmetic sequence
- 1036. Escape the maze
- 1048. The longest string chain
- 105. Construction of binary trees from traversal sequences of preorder and middle order
- 106. Construct binary tree from middle order and post order traversal sequence
- 1072. Flip by column to get the maximum number of equal rows
- 1074. The sum of the elements is the number of submatrixes of the target value
- 1086. The average score of the top five subjects
- 1090. The maximum value affected by the tag
- 1100. The length is K There is no repetition in the string
- 1122. Relative sorting of arrays
- 1123. The closest common ancestor of the deepest leaf node
- 1124. The longest period of good performance
- 1128. Number of equivalent domino pairs
- 1133. Maximum unique number
- 1138. The path on the letterboard
- 1146. Snapshot array
- 1152. Analysis of user's website visiting behavior
- 1153. String conversion
- 1160. spell the words
- 1165. Single keyboard
- 1166. Designing a file system
- 1169. Query invalid transactions
- 1170. Compare the frequency of the smallest letter in a string
- 1171. Delete consecutive nodes with zero sum from the linked list
- 1172. Plate stack
- 1177. Construct palindrome string detection
- 1178. Guess the riddle
- 1181. Front and back stitching
- 1189. “ balloon ” Maximum number of
- 1198. Find the smallest common element in all rows
- 12. Integer to Roman number
- 1202. Exchange elements in a string
- 1207. Unique occurrences
- 1213. The intersection of three ordered arrays
- 1218. The longest definite difference subsequence
- 1224. Maximum equal frequency
- 1244. To make the best of the rankings
- 1248. Statistics 「 Graceful subarray 」
- 1257. The smallest common area
- 1258. Synonym sentence
- 126. The word chain II
- 1261. Look for elements in the contaminated binary tree
- 127. The word chain
- 1275. Find out the winner of tic tac toe
- 128. The longest continuous sequence
- 1282. User groups
- 1296. Divide an array into a set of consecutive numbers
- 1297. The maximum number of substrings
- 13. Roman numeral to integer
- 1311. Get videos your friends have watched
- 133. Clone map
- 1331. Array number conversion
- 1338. Halve the size of the array
- 1345. Jumping game IV
- 1346. Check the existence of integers and their multiples
- 1347. The minimum number of steps to make heterotopic words
- 1348. Tweet count
- 1357. every other n A discount for one customer
- 1358. The number of substrings containing all three characters
- 1365. How many numbers are smaller than the current number
- 1366. Rank the team by voting
- 1370. Up down string
- 1371. Each vowel contains an even number of times the longest substring
- 138. Copy list with random pointer
- 1386. Seating the cinema
- 139. Word splitting
- 1394. Find the lucky number in the array
- 1396. Design the subway system
- 1399. Count the number of the largest groups
- 140. Word splitting II
- 1400. structure K Palindrome strings
- 141. Circular list
- 1410. HTML Entity Resolver
- 1418. Order display form
- 142. Circular list II
- 1426. Number elements
- 1429. The first number
- 1436. Travel terminal
- 1442. The number of triples that form two exclusive or equal arrays
- 1443. The minimum time to collect all the apples on the tree
- 146. LRU cache
- 1460. Make two arrays equal by flipping the rotor array
- 1461. Check whether a string contains all the length of K The binary substring of
- 1477. Find two non overlapping subarrays whose sum is the target value
- 1481. The minimum number of different integers
- 1485. Clone a binary tree with random pointers
- 1487. Make sure the file name is unique
- 1488. Avoid flooding
- 149. The most points on the line
- 1490. clone N Fork tree
- 1496. Determine whether the paths intersect
- 1497. Check whether array pairs can be k to be divisible by
- 1500. Design document sharing system
- 1506. find N The root node of the fork tree
- 1512. A good number of pairs
- 1519. The number of nodes with the same label in the subtree
- 1540. K Operations change string
- 1542. Find the longest favorite substring
- 1546. The maximum number of non empty subarrays with and as the target value and without overlapping
- 1554. A string with only one different character
- 1570. Dot product of two sparse vectors
- 1577. The square of a number is equal to the method number of the product of two numbers
- 159. The longest substring containing at most two different characters
- 1590. Make arrays and can be P to be divisible by
- 1593. Split the string to maximize the number of unique substrings
- 160. Intersecting list
- 1600. The order of succession to the throne
- 1604. Warn people who use the same employee card more than three times in an hour
- 1624. The longest substring between two identical characters
- 1636. Sort the array in ascending order by frequency
- 1638. Count the number of substrings with only one character difference
- 1640. Can you join to form an array
- 1650. The nearest common ancestor of a binary tree III
- 1656. Design ordered flow
- 1657. Determine whether two strings are close to
- 1658. take x Reduced to 0 Minimum operands of
- 166. Fractions to decimals
- 1660. Correct binary tree
- 1674. The minimum number of operations to make arrays complementary
- 1679. K The maximum number of sum pairs
- 1684. Count the number of consistent strings
- 169. Most elements
- 1695. Delete the maximum score of the subarray
- 17. Letter combination of telephone number
- 170. Sum of two numbers III - Data structure design
- 1711. Big meal count
- 1713. Get the minimum number of operations of subsequence
- 1726. Coproduct tuple
- 1737. The minimum number of characters to be changed to satisfy one of the three conditions
- 1740. Find the distance in the binary tree
- 1742. The maximum number of balls in the box
- 1743. Restore an array from a pair of adjacent elements
- 1748. The sum of the only elements
- 1756. Design recently used （MRU） queue
- 1763. The longest nice substring
- 1772. Rank functions by popularity
- 1775. Make the sum of arrays equal by the least number of operations
- 1781. The sum of all substrings
- 1790. Can performing only one string exchange make two strings equal
- 1794. Count the number of substring pairs with the smallest distance
- 1796. The second largest number in a string
- 1797. Design a verification system
- 1804. Realization Trie （ Prefix tree ） II
- 1805. The number of different integers in a string
- 1807. Replace the parentheses in the string
- 1814. Count the number of good pairs in an array
- 1817. Find user active minutes
- 1832. Judge whether the sentence is a full letter sentence
- 1836. Remove duplicate elements from the unsorted linked list
- 1852. The number of types of numbers in each subarray
- 1857. The maximum color value in a directed graph
- 1865. Find the subscript pair for the specified value
- 187. Repetitive DNA Sequence
- 1876. Substrings of three different characters
- 1893. Check that all integers in the region are overwritten
- 1897. Reassign characters so that all strings are equal
- 1906. The minimum value of the absolute value of the query difference
- 1912. Design movie rental system
- 1915. The number of most beautiful substrings
- 1930. The length is 3 Different palindrome subsequences
- 1932. Merge multiple binary search trees
- 1935. The maximum number of words that can be entered
- 1940. Sort the longest common subsequence between arrays
- 1941. Check that all characters appear the same number of times
- 1948. Delete duplicate folders in the system
- 1993. Operations on the tree
- 2001. Number of groups of interchangeable rectangles
- 2006. The absolute value of the difference is K Number to number
- 2007. Restore the original array from the double array
- 2013. Detection square
- 202. Happy number
- 2025. The maximum number of schemes to split the array
- 2032. Values that appear in at least two arrays
- 2034. Stock prices fluctuate
- 2043. Simple banking system
- 205. Isomorphic Strings
- 2053. No K A unique string
- 2062. Count the vowel substrings in the string
- 2068. Check that the two strings are almost equal
- 208. Realization Trie ( Prefix tree )
- 2080. The frequency of querying numbers in the interval
- 2083. Find the total number of substrings beginning and ending with the same letter
- 2085. Count the public strings that appear once
- 2094. find 3 Bit even
- 2099. Find and the maximum length is K The subsequence
- 2103. Ring and rod
- 2107. Share K The number of unique flavors after a candy
- 2115. Find all the dishes you can make from a given raw material
- 2121. The sum of the intervals of the same elements
- 2122. Restore the original array
- 2131. The longest palindrome string obtained by connecting two letter words
- 2133. Check whether each row and column contains all integers
- 2135. Count the number of words you can get by adding letters
- 2150. Find all the numbers in the array
- 2152. The minimum number of lines required to pass through all points
- 2154. Multiply the found value by 2
- 2166. Design bit set
- 2168. The number of unique substrings with the same frequency for each number
- 217. There are duplicate elements
- 2170. The minimum number of operands to make an array an alternating array
- 2186. The minimum number of steps to make two strings into alphabetic ectopic words
- 219. There are duplicate elements II
- 2190. Immediately following in the array key Then the most frequent number
- 2196. Create a binary tree according to the description
- 2201. Statistics of the artifacts that can be extracted
- 2206. Divide the array into equal pairs
- 2215. Find out the difference between the two arrays
- 2225. Find the player who lost zero or one game
- 2227. Encrypt and decrypt strings
- 2244. The minimum number of rounds required to complete all tasks

# 383. Ransom letter

# 997. Find the judge in town

# 229. Find mode II

# 575. Divide candy

# 1054. Bar codes with equal distances

```
class Solution:
def rearrangeBarcodes(self, barcodes: List[int]) -> List[int]:
d, n = Counter(barcodes), len(barcodes)
ans = [0] * n
q = sorted(d.items(), key=lambda x:x[1])
i = 0
for k, v in reversed(q):
for _ in range(v):
ans[i] = k
i += 2
if i >= n: i = 1
return ans
```

```
class Solution {
public int[] rearrangeBarcodes(int[] barcodes) {
Map<Integer, Integer> map = new HashMap<>();
for (int b : barcodes) {
map.put(b, map.getOrDefault(b, 0) + 1);
}
PriorityQueue<int[]> pq = new PriorityQueue<>((a, b) -> (b[1] - a[1]));
for (int k : map.keySet()) {
pq.add(new int[]{
k, map.get(k)});
}
int[] res = new int[barcodes.length];
int i = 0;
while (!pq.isEmpty()) {
int[] temp = pq.poll();
while (temp[1] -- > 0) {
res[i] = temp[0];
i += 2;
if (i >= barcodes.length) i = 1;
}
}
return res;
}
}
```

# 560. And for K Subarray

```
class Solution:
def subarraySum(self, nums: List[int], k: int) -> int:
res, acc, d = 0, 0, {
}
for x in nums:
d[acc] = d.get(acc, 0) + 1
acc += x
res += d.get(acc - k, 0)
return res
```

```
class Solution {
public int subarraySum(int[] nums, int k) {
int res = 0, acc = 0;
Map<Integer, Integer> map = new HashMap<>();
for (int i = 0; i < nums.length; i++){
map.put(acc, map.getOrDefault(acc, 0) + 1);
acc += nums[i];
res += map.getOrDefault(acc - k, 0);
}
return res;
}
}
```

# 41. First positive number missing

```
class Solution:
def firstMissingPositive(self, nums: List[int]) -> int:
n = len(nums)
m = n + 1
# Preprocessing negative numbers >n Number of numbers
for i in range(n):
x = nums[i]
if x > n or x < 0:
nums[i] = 0
# Mark + m
for i in range(n):
x = nums[i] % m # Restore
if x > 0: nums[x-1] += m
for i in range(n):
if nums[i] < m: return i+1
return m
```

# 242. Effective alphabetic words

# 244. The shortest word distance II

# 246. Centrosymmetric number

# 249. Shift string grouping

# 264. Ugly number II

# 266. Palindrome arrangement

# 267. Palindrome arrangement II

# 268. Missing numbers

# 76. Minimum cover substring

# 288. The only abbreviation of a word

# 290. Rules of words

```
class Solution:
def wordPattern(self, pattern: str, s: str) -> bool:
words = s.split()
d = {
}
if len(words) != len(pattern):return False
for i, c in enumerate(pattern):
w = words[i]
if c not in d: d[c] = w
elif d[c] != w: return False
if len(d) != len(set(words)): return False
return True
```

# 291. Rules of words II

# 299. Guess the number game

# 3. Longest substring without repeating characters

# 30. Concatenate the substrings of all words

# 311. Multiplication of sparse matrices

# 313. Super ugly number

# 314. Vertical traversal of binary trees

# 325. And equal to k The longest subarray length of

# 336. The palindrome is right

# 340. At most K Longest substring of different characters

# 347. front K High frequency elements

# 348. Design tic tac toe chess

# 349. Intersection of two arrays

# 350. Intersection of two arrays II

# 355. Design twitter

# 356. Line mirror image

# 358. K The distance interval rearranges the string

# 359. Log rate limiter

# 36. Effective Sudoku

# 362. Hit the counter

# 379. Telephone directory management system

# 380. O(1) Time insertion 、 Delete and get random elements

# 381. O(1) Time insertion 、 Delete and get random elements - Allow repetition

# 387. The first unique character in the string

# 395. There are at least K The longest substring of repeated characters

# 398. Random number index

# 409. Longest palindrome

# 421. The maximum exclusive or value of two numbers in an array

# 423. Reconstructing Chinese from English

# 424. The longest repeated character after replacement

# 432. whole O(1) Data structure of

# 433. Minimal genetic change

# 438. Find all alphabetic words in the string

# 442. Duplicate data in array

# 447. The number of boomerangs

# 448. Find all the missing numbers in the array

# 451. Sort the characters according to their frequency of occurrence

# 454. Add four numbers II

# 457. Whether there is a loop in the ring array

# 460. LFU cache

# 480. Sliding window median

# 49. Letter heterotopic word grouping

# 491. Increasing subsequence

# 496. Next bigger element I

# 500. Keyboard line

# 508. The most frequent sub tree elements and

# 519. Random flip matrix

# 522. The longest special sequence II

# 523. Continuous subarrays and

# 531. Lonely pixels I

# 532. Array k-diff Number pair

# 533. Lonely pixels II

# 535. TinyURL Encryption and decryption

# 567. Arrangement of strings

# 582. Kill the process

# 588. Design memory file system

# 594. The longest harmonious subsequence

# 599. The minimum index sum of two lists

# 604. Iteratively compress strings

# 609. Find duplicate files in the system

# 616. Add bold tags to strings

# 621. Task scheduler

# 632. Minimum range

# 635. Design the log storage system

# 645. The wrong set

# 652. Look for duplicate subtrees

# 653. Sum of two numbers IV - Input BST

# 659. Split the array into successive subsequences

# 676. Implement a magic dictionary

# 677. Key value mapping

# 690. The importance of employees

# 692. front K High frequency words

# 694. The number of different islands

# 697. The degree of the array

# 705. Design hash sets

# 706. Design hash map

# 710. Random numbers in the blacklist

# 711. The number of different islands II

# 720. The longest word in the dictionary

# 726. The number of atoms

# 73. Matrix zeroing

# 734. Sentence similarity

# 736. Lisp Syntax parsing

# 737. Sentence similarity II

# 740. Delete and get points

# 748. The shortest complement

# 752. Open the turntable lock

# 758. Bold words in strings

# 760. Find the displacement map

# 763. Division of alphabet

# 767. Refactoring strings

# 770. Basic calculator IV

# 771. Gems and stones

# 791. Custom string sorting

# 792. Number of words to match subsequence

# 804. The only Morse code word

# 811. Subdomain access count

# 815. Bus routes

# 817. Linked list component

# 819. The most common word

# 820. Compression coding of words

# 822. Flip card game

# 823. Binary trees with factors

# 859. Intimate string

# 865. The smallest subtree with all the deepest nodes

# 868. Binary spacing

# 873. The length of the longest Fibonacci subsequence

# 884. Unusual words in two sentences

# 889. Construct binary tree according to preorder and postorder traversal

# 890. Find and replace patterns

# 893. Special equivalent string group

# 895. Maximum frequency stack

# 911. Online elections

# 916. Word subsets

# 923. Many possibilities of the sum of three

# 929. Unique email address

# 930. And the same binary subarray

# 939. Minimum area rectangle

# 953. Verification of an alien language dictionary

# 954. Double pair array

# 957. N After the day of

# 961. In length 2N Find duplicates in the array of N Secondary elements

# 966. Vowel spelling checker

# 970. Strong integer

# 974. And can be K A subarray of integers

# 981. Time based key value storage

# 982. A triple with a bitwise and zero

# 987. The vertical traversal of a binary tree

# 992. K Sub array of different integers

# 1001. Grid lighting

# 1002. Find common characters

# 1010. The total duration can be 60 The song of division

# 1015. Can be K The smallest integer that is divisible

# 1027. The longest arithmetic sequence

# 1036. Escape the maze

# 1048. The longest string chain

# 105. Construction of binary trees from traversal sequences of preorder and middle order

# 106. Construct binary tree from middle order and post order traversal sequence

# 1072. Flip by column to get the maximum number of equal rows

# 1074. The sum of the elements is the number of submatrixes of the target value

# 1086. The average score of the top five subjects

# 1090. The maximum value affected by the tag

# 1100. The length is K There is no repetition in the string

# 1122. Relative sorting of arrays

# 1123. The closest common ancestor of the deepest leaf node

# 1124. The longest period of good performance

# 1128. Number of equivalent domino pairs

# 1133. Maximum unique number

# 1138. The path on the letterboard

# 1146. Snapshot array

# 1152. Analysis of user's website visiting behavior

# 1153. String conversion

# 1160. spell the words

# 1165. Single keyboard

# 1166. Designing a file system

# 1169. Query invalid transactions

# 1170. Compare the frequency of the smallest letter in a string

# 1171. Delete consecutive nodes with zero sum from the linked list

# 1172. Plate stack

# 1177. Construct palindrome string detection

# 1178. Guess the riddle

# 1181. Front and back stitching

# 1189. “ balloon ” Maximum number of

# 1198. Find the smallest common element in all rows

# 12. Integer to Roman number

# 1202. Exchange elements in a string

# 1207. Unique occurrences

# 1213. The intersection of three ordered arrays

# 1218. The longest definite difference subsequence

# 1224. Maximum equal frequency

# 1244. To make the best of the rankings

# 1248. Statistics 「 Graceful subarray 」

# 1257. The smallest common area

# 1258. Synonym sentence

# 126. The word chain II

# 1261. Look for elements in the contaminated binary tree

# 127. The word chain

# 1275. Find out the winner of tic tac toe

# 128. The longest continuous sequence

# 1282. User groups

# 1296. Divide an array into a set of consecutive numbers

# 1297. The maximum number of substrings

# 13. Roman numeral to integer

# 1311. Get videos your friends have watched

# 133. Clone map

# 1331. Array number conversion

# 1338. Halve the size of the array

# 1345. Jumping game IV

# 1346. Check the existence of integers and their multiples

# 1347. The minimum number of steps to make heterotopic words

# 1348. Tweet count

# 1357. every other n A discount for one customer

# 1358. The number of substrings containing all three characters

# 1365. How many numbers are smaller than the current number

# 1366. Rank the team by voting

# 1370. Up down string

# 1371. Each vowel contains an even number of times the longest substring

# 138. Copy list with random pointer

# 1386. Seating the cinema

# 139. Word splitting

# 1394. Find the lucky number in the array

# 1396. Design the subway system

# 1399. Count the number of the largest groups

# 140. Word splitting II

# 1400. structure K Palindrome strings

# 141. Circular list

# 1410. HTML Entity Resolver

# 1418. Order display form

# 142. Circular list II

# 1426. Number elements

# 1429. The first number

# 1436. Travel terminal

# 1442. The number of triples that form two exclusive or equal arrays

# 1443. The minimum time to collect all the apples on the tree

# 146. LRU cache

# 1460. Make two arrays equal by flipping the rotor array

# 1461. Check whether a string contains all the length of K The binary substring of

# 1477. Find two non overlapping subarrays whose sum is the target value

# 1481. The minimum number of different integers

# 1485. Clone a binary tree with random pointers

# 1487. Make sure the file name is unique

# 1488. Avoid flooding

# 149. The most points on the line

# 1490. clone N Fork tree

# 1496. Determine whether the paths intersect

# 1497. Check whether array pairs can be k to be divisible by

# 1500. Design document sharing system

# 1506. find N The root node of the fork tree

# 1512. A good number of pairs

# 1519. The number of nodes with the same label in the subtree

# 1540. K Operations change string

# 1542. Find the longest favorite substring

# 1546. The maximum number of non empty subarrays with and as the target value and without overlapping

# 1554. A string with only one different character

# 1570. Dot product of two sparse vectors

# 1577. The square of a number is equal to the method number of the product of two numbers

# 159. The longest substring containing at most two different characters

# 1590. Make arrays and can be P to be divisible by

# 1593. Split the string to maximize the number of unique substrings

# 160. Intersecting list

# 1600. The order of succession to the throne

# 1604. Warn people who use the same employee card more than three times in an hour

# 1624. The longest substring between two identical characters

# 1636. Sort the array in ascending order by frequency

# 1638. Count the number of substrings with only one character difference

# 1640. Can you join to form an array

# 1650. The nearest common ancestor of a binary tree III

# 1656. Design ordered flow

# 1657. Determine whether two strings are close to

# 1658. take x Reduced to 0 Minimum operands of

# 166. Fractions to decimals

# 1660. Correct binary tree

# 1674. The minimum number of operations to make arrays complementary

# 1679. K The maximum number of sum pairs

# 1684. Count the number of consistent strings

# 169. Most elements

# 1695. Delete the maximum score of the subarray

# 17. Letter combination of telephone number

# 170. Sum of two numbers III - Data structure design

# 1711. Big meal count

# 1713. Get the minimum number of operations of subsequence

# 1726. Coproduct tuple

# 1737. The minimum number of characters to be changed to satisfy one of the three conditions

# 1740. Find the distance in the binary tree

# 1742. The maximum number of balls in the box

# 1743. Restore an array from a pair of adjacent elements

# 1748. The sum of the only elements

# 1756. Design recently used （MRU） queue

# 1763. The longest nice substring

# 1772. Rank functions by popularity

# 1775. Make the sum of arrays equal by the least number of operations

# 1781. The sum of all substrings

# 1790. Can performing only one string exchange make two strings equal

# 1794. Count the number of substring pairs with the smallest distance

# 1796. The second largest number in a string

# 1797. Design a verification system

# 1804. Realization Trie （ Prefix tree ） II

# 1805. The number of different integers in a string

# 1807. Replace the parentheses in the string

# 1814. Count the number of good pairs in an array

# 1817. Find user active minutes

# 1832. Judge whether the sentence is a full letter sentence

# 1836. Remove duplicate elements from the unsorted linked list

# 1852. The number of types of numbers in each subarray

# 1857. The maximum color value in a directed graph

# 1865. Find the subscript pair for the specified value

# 187. Repetitive DNA Sequence

# 1876. Substrings of three different characters

# 1893. Check that all integers in the region are overwritten

# 1897. Reassign characters so that all strings are equal

# 1906. The minimum value of the absolute value of the query difference

# 1912. Design movie rental system

# 1915. The number of most beautiful substrings

# 1930. The length is 3 Different palindrome subsequences

# 1932. Merge multiple binary search trees

# 1935. The maximum number of words that can be entered

# 1940. Sort the longest common subsequence between arrays

# 1941. Check that all characters appear the same number of times

# 1948. Delete duplicate folders in the system

# 1993. Operations on the tree

# 2001. Number of groups of interchangeable rectangles

# 2006. The absolute value of the difference is K Number to number

# 2007. Restore the original array from the double array

# 2013. Detection square

# 202. Happy number

# 2025. The maximum number of schemes to split the array

# 2032. Values that appear in at least two arrays

# 2034. Stock prices fluctuate

# 2043. Simple banking system

# 205. Isomorphic Strings

# 2053. No K A unique string

# 2062. Count the vowel substrings in the string

# 2068. Check that the two strings are almost equal

# 208. Realization Trie ( Prefix tree )

# 2080. The frequency of querying numbers in the interval

# 2083. Find the total number of substrings beginning and ending with the same letter

# 2085. Count the public strings that appear once

# 2094. find 3 Bit even

# 2099. Find and the maximum length is K The subsequence

# 2103. Ring and rod

# 2107. Share K The number of unique flavors after a candy

# 2115. Find all the dishes you can make from a given raw material

# 2121. The sum of the intervals of the same elements

# 2122. Restore the original array

# 2131. The longest palindrome string obtained by connecting two letter words

# 2133. Check whether each row and column contains all integers

# 2135. Count the number of words you can get by adding letters

# 2150. Find all the numbers in the array

# 2152. The minimum number of lines required to pass through all points

# 2154. Multiply the found value by 2

# 2166. Design bit set

# 2168. The number of unique substrings with the same frequency for each number

# 217. There are duplicate elements

# 2170. The minimum number of operands to make an array an alternating array

# 2186. The minimum number of steps to make two strings into alphabetic ectopic words

# 219. There are duplicate elements II

# 2190. Immediately following in the array key Then the most frequent number

# 2196. Create a binary tree according to the description

# 2201. Statistics of the artifacts that can be extracted

# 2206. Divide the array into equal pairs

# 2215. Find out the difference between the two arrays

# 2225. Find the player who lost zero or one game

# 2227. Encrypt and decrypt strings

# 2244. The minimum number of rounds required to complete all tasks

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author[Yake1965],Please bring the original link to reprint, thank you.

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