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LeetCode -> NeetCode
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  • 100. Same Tree
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  • 1041. Robot Bounded In Circle
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  • 105. Construct Binary Tree from Preorder and Inorder Traversal
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  • 11. Container With Most Water
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  • 116. Populating Next Right Pointers in Each Node
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  • 1448. Count Good Nodes in Binary Tree
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  • 146. LRU Cache
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  • 15. 3Sum
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  • 150. Evaluate Reverse Polish Notation
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  • 152. Maximum Product Subarray
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  • 1539. Kth Missing Positive Number
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  • 155. Min Stack
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  • 1584. Min Cost to Connect All Points
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  • 162. Find Peak Element
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  • 167. Two Sum II - Input Array Is Sorted
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  • 17. Letter Combinations of a Phone Number
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  • 19. Remove Nth Node From End of List
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  • 198. House Robber
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  • 199. Binary Tree Right Side View
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  • 2. Add Two Numbers
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  • 20. Valid Parentheses
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  • 21. Merge Two Sorted Lists
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  • 215. Kth Largest Element in an Array
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  • 226. Invert Binary Tree
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  • 23. Merge k Sorted Lists
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  • 230. Kth Smallest Element in a BST
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  • 235. Lowest Common Ancestor of a Binary Search Tree
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  • 239. Sliding Window Maximum
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  • 252-meeting-rooms
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  • 253-meeting-rooms-ii
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  • 268. Missing Number
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  • 287. Find the Duplicate Number
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  • 295. Find Median from Data Stream
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  • 3. Longest Substring Without Repeating Characters
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  • 322. Coin Change
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  • 33. Search in Rotated Sorted Array
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  • 338. Counting Bits
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  • 347. Top K Frequent Elements
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  • 35. Search Insert Position
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  • 355. Design Twitter
    • CODE
  • 36. Valid Sudoku
    • CODE
  • 371. Sum of Two Integers
    • CODE
  • 378. Kth Smallest Element in a Sorted Matrix
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  • 39. Combination Sum
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  • 4. Median of Two Sorted Arrays
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  • 40. Combination Sum II
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  • 417-pacific-atlantic-water-flow
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  • 42-trapping-rain-water
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  • 424. Longest Repeating Character Replacement
    • CODE
  • 43. Multiply Strings
    • CODE
  • 435. Non-overlapping Intervals
    • CODE
  • 436. Find Right Interval
    • CODE
  • 442. Find All Duplicates in an Array
    • CODE
  • 448. Find All Numbers Disappeared in an Array
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  • 45. Jump Game II
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  • 46. Permutations
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  • 47. Permutations II
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  • 48. Rotate Image
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  • 49. Group Anagrams
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  • 5. Longest Palindromic Substring
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  • 50. Pow(x, n)
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  • 51. N-Queens
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  • 53. Maximum Subarray
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  • 54. Spiral Matrix
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  • 543. Diameter of Binary Tree
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  • 547. Number of Provinces
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  • 55. Jump Game
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  • 554. Brick Wall
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  • 56. Merge Intervals
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  • 567. Permutation in String
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  • 57. Insert Interval
    • CODE
  • 572. Subtree of Another Tree
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  • 581. Shortest Unsorted Continuous Subarray
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  • 61. Rotate List
    • CODE
  • 62. Unique Paths
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  • 621. Task Scheduler
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  • 647. Palindromic Substrings
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  • 659 · Encode and Decode Strings
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  • 66. Plus One
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  • 695. Max Area of Island
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  • 7. Reverse Integer
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  • 70. Climbing Stairs
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  • 703. Kth Largest Element in a Stream
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  • 704. Binary Search
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  • 73-set-matrix-zeroes
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  • 739. Daily Temperatures
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  • 74. Search a 2D Matrix
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  • 746. Min Cost Climbing Stairs
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  • 75. Sort Colors
    • CODE
  • 76-minimum-window-substring
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  • 763. Partition Labels
    • CODE
  • 78. Subsets
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  • 784. Letter Case Permutation
    • CODE
  • 79. Word Search
    • CODE
  • 796. Rotate String
    • CODE
  • 828. Count Unique Characters of All Substrings of a Given String
    • CODE
  • 832. Flipping an Image
    • CODE
  • 84. Largest Rectangle in Histogram
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  • 846. Hand of Straights
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  • 853. Car Fleet
  • 875. Koko Eating Bananas
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  • 90. Subsets II
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  • 904. Fruit Into Baskets
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  • 91. Decode Ways
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  • 973. K Closest Points to Origin
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  • 977. Squares of a Sorted Array
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  • 98. Validate Binary Search Tree
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  • 981-time-based-key-value-store
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  • 993. Cousins in Binary Tree
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  • 994. Rotting Oranges
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355. Design Twitter

Medium

Design a simplified version of Twitter where users can post tweets, follow/unfollow another user, and is able to see the 10 most recent tweets in the user's news feed.

Implement the Twitter class:

  • Twitter() Initializes your twitter object.

  • void postTweet(int userId, int tweetId) Composes a new tweet with ID tweetId by the user userId. Each call to this function will be made with a unique tweetId.

  • List<Integer> getNewsFeed(int userId) Retrieves the 10 most recent tweet IDs in the user's news feed. Each item in the news feed must be posted by users who the user followed or by the user themself. Tweets must be ordered from most recent to least recent.

  • void follow(int followerId, int followeeId) The user with ID followerId started following the user with ID followeeId.

  • void unfollow(int followerId, int followeeId) The user with ID followerId started unfollowing the user with ID followeeId.

Example 1:

Input
["Twitter", "postTweet", "getNewsFeed", "follow", "postTweet", "getNewsFeed", "unfollow", "getNewsFeed"]
[[], [1, 5], [1], [1, 2], [2, 6], [1], [1, 2], [1]]
Output
[null, null, [5], null, null, [6, 5], null, [5]]

Explanation
Twitter twitter = new Twitter();
twitter.postTweet(1, 5); // User 1 posts a new tweet (id = 5).
twitter.getNewsFeed(1);  // User 1's news feed should return a list with 1 tweet id -> [5]. return [5]
twitter.follow(1, 2);    // User 1 follows user 2.
twitter.postTweet(2, 6); // User 2 posts a new tweet (id = 6).
twitter.getNewsFeed(1);  // User 1's news feed should return a list with 2 tweet ids -> [6, 5]. Tweet id 6 should precede tweet id 5 because it is posted after tweet id 5.
twitter.unfollow(1, 2);  // User 1 unfollows user 2.
twitter.getNewsFeed(1);  // User 1's news feed should return a list with 1 tweet id -> [5], since user 1 is no longer following user 2.

Constraints:

  • 1 <= userId, followerId, followeeId <= 500

  • 0 <= tweetId <= 104

  • All the tweets have unique IDs.

  • At most 3 * 104 calls will be made to postTweet, getNewsFeed, follow, and unfollow.

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Last updated 2 years ago