LeetCode Summary by Topics
Collection of summarized notes and key problem-solving techniques for various LeetCode topics.
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Full list of Leetcode questions
Array
Array questions
Leetcode Day 1 - Array Basics
Focuses on fundamental array operations. Covers binary search and basic element removal, emphasizing efficient searching and modifying arrays.
Leetcode Day 2 - Advanced Array Manipulation
More advanced array techniques, including sliding window to find the minimum subarray sum and generating a matrix in a spiral order, which requires managing more complex array structures.
Linked List
Linked List questions
Leetcode Day 3 - Linked List Basics
Introduces fundamental linked list operations. Topics include removing elements from a list, designing a custom linked list with core operations, and reversing a singly linked list, highlighting ba...
Leetcode Day 4 - Advanced Linked List Operations
Focuses on more complex linked list problems, such as swapping nodes in pairs, removing nodes from specific positions, detecting intersections between two lists, and identifying cycles within a lin...
Hash Table
Hash Table questions
Leetcode Day 5 - Hash Table Basics
Covers the basics of hash table usage, including checking for anagrams, finding intersections of arrays, identifying happy numbers, and solving the classic two-sum problem. Focus is on efficient lo...
Leetcode Day 6 - Advanced Hash Table
Focuses on more complex problems involving hash tables, such as multi-array sum combinations (4Sum II, 3Sum, 4Sum) and validating ransom note creation. These problems require more intricate use of ...
String
String questions
Leetcode Day 7 - String Reversal and Manipulation Basics
Description: Focuses on basic string reversal techniques and simple string manipulations. Includes reversing strings and segments of strings, along with replacing numbers in a string.
Leetcode Day 8 - Advanced String Manipulations & KMP
Involves more advanced string operations, such as reversing the order of words, finding the first occurrence of a substring, identifying repeated patterns, and handling right-handed string manipula...
Stack and Queue
Stack and Queue questions
Leetcode Day 9 - Stack & Queue Fundamentals
Focuses on basic stack and queue operations, including implementing one data structure using the other. Also covers classic stack usage in problems like validating parentheses and removing adjacent...
Leetcode Day 10 - Advanced Stack & Queue Applications
Description: Explores advanced applications of stacks and queues, such as evaluating reverse Polish notation, finding the maximum in a sliding window, and using heaps/queues to find the top K frequ...
Binary Tree
Binary Tree questions
Leetcode Day 11 - Binary Tree: Traversal Techniques
Focuses on binary tree level order traversal techniques, including regular, N-ary tree, and right-side view traversals. Also calculates averages at each tree level.
Leetcode Day 12 - Binary Tree: Tree Structure and Depth
Involves manipulating binary tree structures, such as inverting a binary tree and determining symmetry. Also covers finding the maximum and minimum depth of a tree.
Leetcode Day 13 - Binary Tree: Tree Balance and Paths
Examines binary tree balance (height-balanced trees), finding all root-to-leaf paths, summing left leaves, and counting nodes in complete trees.
Leetcode Day 14 - Binary Tree: Path and Construction Problems
Focuses on finding specific nodes or values in binary trees, such as the bottom-left value and path sums. Also covers reconstructing binary trees from inorder and postorder traversal.
Leetcode Day 15 - Binary Tree: Construction and Search Operations
Emphasizes constructing and manipulating binary trees, including building the maximum binary tree, merging trees, and performing search and validation operations in binary search trees (BST).
Leetcode Day 16 - Binary Tree: Binary Search Tree Special Cases
Concentrates on binary search tree (BST)-specific problems, such as finding the minimum absolute difference, locating the mode, and identifying the lowest common ancestor in both binary and binary ...
Leetcode Day 17 - Binary Search Tree: Insertion, Deletion, and LCA
Focuses on essential binary search tree (BST) operations, including finding the lowest common ancestor, inserting new nodes, and deleting nodes from a BST while maintaining its properties.
Leetcode Day 18 - Binary Search Tree: Transformations and Conversions
Examines BST transformations, such as trimming a tree within a given range, converting a sorted array into a balanced BST, and converting a BST to a greater tree by modifying its node values.
Backtracking
Backtracking questions
Leetcode Day 19 - Backtracking: Combination
77 Combinations | 216 Combination Sum III |17 Letter Combinations of a Phone Number
Leetcode Day 20 - Backtracking: Cutting
39 Combination Sum | 40 Combination Sum II | 131 Palindrome Partitioning
Leetcode Day 21 - Backtracking: Subsets
93 Restore IP Addresses | 78 Subsets | 90 Subsets II
Leetcode Day 22 - Backtracking: Permutation & Chessboard
491 Non-decreasing Subsequences | 46 Permutations | 47 Permutations II | 332 Reconstruct Itinerary | 51 N-Queens | 37 Sudoku Solver
Greedy
Greedy questions
Leetcode Day 23 - Greedy: Basic Applications
Fundamental greedy problems: 455 Assign Cookies | 376 Wiggle Subsequence | 53 Maximum Subarray
Leetcode Day 24 - Greedy: Stock and Jump Problems
122 Best Time to Buy and Sell Stock II | 55 Jump Game | 45 Jump Game II | 1005 Maximize Sum Of Array After K Negations
Leetcode Day 25 - Greedy: Two-Dimensional Trade-Off
134 Gas Station | 135 Candy | 860 Lemonade Change | 406 Queue Reconstruction by Height
Leetcode Day 26 - Greedy: Overlapping Intervals
452 Minimum Number of Arrows to Burst Balloons | 435 Non-overlapping Intervals | 763 Partition Labels
Leetcode Day 27 - Greedy: Advanced Interval & Sequence Problems
56 Merge Intervals | 738 Monotone Increasing Digits | 968 Binary Tree Cameras
Dynamic Programming
Dynamic Programming questions
Leetcode 28 - Dynamic Programming
509 Fibonacci Number | 70 Climbing Stairs | 746 Min Cost Climbing Stairs
Leetcode Day 29 - Dynamic Programming
62 Unique Paths | 63 Unique Paths II | 343 Integer Break | 96 Unique Binary Search Trees
Leetcode Day 30 - DP : Backpack Problem Basic
背包问题基础，二维dp数组、一维dp数组（滚动数组）
Leetcode Day 31 - Dynamic Programming
416 Partition Equal Subset Sum | 1049 Last Stone Weight II | 494 Target Sum ｜ 474 Ones and Zeroes
Leetcode Day 32 - DP: Complete Knapsack Problem
Kama 52 Complete Knapsack | 518 Coin Change II | 377 Combination Sum IV | Kama 57 Climbing Stairs
Leetcode Day 33 - DP: Multiple Knapsack Problem
322 Coin Change | 279 Perfect Squares | 139 Word Break
Leetcode Day 34 - DP: House Robber
198 House Robber | 213 House Robber II | 337 House Robber III
Leetcode Day 35 - DP: Buy and Sell Stock
121 Best Time to Buy and Sell Stock ｜ 122 Best Time to Buy and Sell Stock II | 123 Best Time to Buy and Sell Stock III
Leetcode Day 36 - DP: Buy and Sell Stock Advanced
188 Best Time to Buy and Sell Stock IV ｜ 309 Best Time to Buy and Sell Stock with Cooldown | 714 Best Time to Buy and Sell Stock with Transaction Fee
Leetcode Day 37 - DP: Subsequence
300 Longest Increasing Subsequence | 674 Longest Continuous Increasing Subsequence | 18 Maximum Length of Repeated Subarray
Leetcode Day 38 - DP: Subsequence
1143 Longest Common Subsequence | 1035 Uncrossed Lines | 53 Maximum Subarray | 392 Is Subsequence
Leetcode Day 39 - DP: Subsequence
115 Distinct Subsequences | 583 Delete Operation for Two Strings | 72 Edit Distance
Leetcode Day 40 - DP: Palindromic Subsequence
647 Palindromic Substrings | 516 Longest Palindromic Subsequence
Monotone stack
Monotone stack questions
Leetcode Day 41 - Monotone stack
Monotone stack Diff Problem Python Java 121 Best Time to Buy and Sell Stock 19 Remove Nth Node ...
Leetcode Day 41 - Monotone stack
739 Daily Temperatures | 496 Next Greater Element I | 503 Next Greater Element II
Leetcode Day 42 - Monotone stack Advanced
42 Trapping Rain Water | 84 Largest Rectangle in Histogram