LeetCode Questions List
LeetCode Questions List
This page contains a comprehensive list of all LeetCode problems solved in this blog, organized by difficulty level, category, and solution approach.
Summary Statistics
- Total Posts: 253 (LC problem posts)
- Easy: 43 problems
- Medium: 177 problems
- Hard: 33 problems
All LeetCode Problems
Problems by Difficulty
Easy (43 problems)
See the All LeetCode Problems table above for the full list with links.
Medium (177 problems)
See the All LeetCode Problems table above for the full list with links. Sample:
- 3. Longest Substring Without Repeating Characters
- 23. Swap Nodes in Pairs
- 33. Search in Rotated Sorted Array
- 46. Permutations
- 47. Permutations II
- 48. Rotate Image
- 394. Decode String
- 50. Pow(x, n)
- 54. Spiral Matrix
- 62. Unique Paths
- 695. Max Area of Island
- 77. Combinations
- 89. Gray Code
- 96. Unique Binary Search Trees
- 131. Palindrome Partitioning
- 1443. Minimum Time to Collect All Apples in a Tree
- 1650. Lowest Common Ancestor of a Binary Tree III
- 150. Evaluate Reverse Polish Notation
- 240. Search a 2D Matrix II
- 300. Longest Increasing Subsequence
- 316. Remove Duplicate Letters
- 406. Queue Reconstruction by Height
- 417. Pacific Atlantic Water Flow
- 437. Path Sum III
- 494. Target Sum
- 503. Next Greater Element II
- 636. Exclusive Time of Functions
- 648. Replace Words
- 708. Insert into a Sorted Circular Linked List
- 863. All Nodes Distance K in Binary Tree
- 912. Sort an Array
- 990. Satisfiability of Equality Equations
- 1124. Longest Well-Performing Interval
- 1242. Web Crawler Multithreaded
- 1570. Dot Product of Two Sparse Vectors
- 1856. Maximum Sum of Minimum Product
- 1865. Finding Pairs With a Certain Sum
- 1868. Product of Two Run-Length Encoded Arrays
- 187. Repeated DNA Sequences
- 2043. Simple Bank System
- 2466. Count Ways To Build Good Strings
- 2799. Count Complete Subarrays in an Array
- 794. Valid Tic-Tac-Toe State
- 973. K Closest Points to Origin
Hard (33 problems)
See the All LeetCode Problems table above for the full list with links.
(Below: sample links from the original curated list.)
- 25. Reverse Nodes in k-Group
- 84. Largest Rectangle in Histogram
- 218. The Skyline Problem
- 317. Shortest Distance from All Buildings
Problems by Category
Array & Matrix
- 33. Search in Rotated Sorted Array - Binary Search
- 48. Rotate Image - Matrix Rotation
- 54. Spiral Matrix - Simulation
- 62. Unique Paths - DP, Combinatorics
- 695. Max Area of Island - DFS, Connected Components
- 240. Search a 2D Matrix II - Binary Search, Divide & Conquer
- 300. Longest Increasing Subsequence - DP, Binary Search
- 406. Queue Reconstruction by Height - Greedy, Sorting
- 417. Pacific Atlantic Water Flow - DFS, BFS
- 494. Target Sum - DP, Subset Sum
- 503. Next Greater Element II - Monotonic Stack
- 912. Sort an Array - Merge Sort, Heap Sort, Counting Sort
- 1124. Longest Well-Performing Interval - Hash Map, Prefix Sum
- 1856. Maximum Sum of Minimum Product - Monotonic Stack, Prefix Sum
- 2799. Count Complete Subarrays in an Array - Sliding Window, Hash Map
- 1094. Car Pooling - Bucket Sort, Event Processing
- 1207. Unique Number of Occurrences - Hash Map, Hash Set
- 347. Top K Frequent Elements - Bucket Sort, Quickselect, Heap
- 419. Battleships in a Board - Top-Left Corner, DFS
- 973. K Closest Points to Origin - Sorting, Heap, Quickselect
String Processing
- 3. Longest Substring Without Repeating Characters - Hash Map, Two Pointers
- 187. Repeated DNA Sequences - Rolling Hash, Bit Encoding
- 316. Remove Duplicate Letters - Monotonic Stack, Greedy
- 394. Decode String - Stack, String Processing
- 648. Replace Words - Trie, Hash Set
- 794. Valid Tic-Tac-Toe State - Simulation, Validation
- 1249. Minimum Remove to Make Valid Parentheses - Stack Validation, Parentheses
Linked List
- 23. Swap Nodes in Pairs - Recursion, Iteration
- 25. Reverse Nodes in k-Group - Recursion, Iteration
- 708. Insert into a Sorted Circular Linked List - Two Pointers, Circular List
Tree & DFS
- 314. Binary Tree Vertical Order Traversal - BFS, Level Order
- 426. Convert Binary Search Tree to Sorted Doubly Linked List - Inorder Traversal, Recursion
- 437. Path Sum III - DFS, Recursion
- 545. Boundary of Binary Tree - DFS, Boundary Traversal
- 863. All Nodes Distance K in Binary Tree - Graph Conversion, DFS, Parent Pointer
- 1443. Minimum Time to Collect All Apples in a Tree - DFS, Tree Traversal
- 1650. Lowest Common Ancestor of a Binary Tree III - Two Pointers, Tree Traversal
Dynamic Programming
- 62. Unique Paths - DP, Combinatorics
- 96. Unique Binary Search Trees - DP, Catalan Numbers
- 300. Longest Increasing Subsequence - DP, Binary Search
- 494. Target Sum - DP, Subset Sum
- 2466. Count Ways To Build Good Strings - DP, Bottom-up, Top-down
Backtracking
- 46. Permutations - Backtracking, STL
- 47. Permutations II - Backtracking, STL, Duplicates
- 77. Combinations - Backtracking
- 131. Palindrome Partitioning - Backtracking, DFS
Stack & Queue
- 84. Largest Rectangle in Histogram - Monotonic Stack
- 150. Evaluate Reverse Polish Notation - Stack
- 316. Remove Duplicate Letters - Monotonic Stack, Greedy
- 636. Exclusive Time of Functions - Stack, Log Parsing
- 503. Next Greater Element II - Monotonic Stack
- 1856. Maximum Sum of Minimum Product - Monotonic Stack, Prefix Sum
Graph & Union Find
- 417. Pacific Atlantic Water Flow - DFS, BFS
- 863. All Nodes Distance K in Binary Tree - Graph Conversion, DFS, Parent Pointer
- 990. Satisfiability of Equality Equations - Union Find, DFS
- 317. Shortest Distance from All Buildings - BFS, Multi-source
Data Structure Design
- 1570. Dot Product of Two Sparse Vectors - Hash Map, Optimization
- 1865. Finding Pairs With a Certain Sum - Hash Map, Count Tracking
- 2043. Simple Bank System - Data Structure Design
- 348. Design Tic-Tac-Toe - Counter Optimization, State Tracking
Advanced Algorithms
- 218. The Skyline Problem - Sweep Line, Priority Queue
- 1242. Web Crawler Multithreaded - Multithreading, BFS
Math & Bit Manipulation
- 50. Pow(x, n) - Fast Exponentiation
- 89. Gray Code - Bit Manipulation
Run-Length Encoding
- 1868. Product of Two Run-Length Encoded Arrays - Two Pointers, Array Processing
Solution Approaches Summary
Most Common Approaches
- Dynamic Programming (DP) - 5 problems
- Monotonic Stack - 4 problems
- Binary Search - 4 problems
- Hash Map/Set - 6 problems
- DFS/BFS - 5 problems
- Backtracking - 2 problems
- Sliding Window - 2 problems
- Two Pointers - 2 problems
- Trie - 1 problem
- Union Find - 1 problem
- Sweep Line - 1 problem
- Data Structure Design - 2 problems
Algorithm Patterns
- Array Processing: Sliding window, two pointers, prefix sum
- String Processing: Trie, hash map, monotonic stack
- Graph Traversal: DFS, BFS, Union Find
- Optimization: Dynamic programming, greedy algorithms
- Data Structures: Stack, queue, heap, trie
- Search: Binary search, divide and conquer
Recent Additions
Latest Problems (February 2026)
- 187. Repeated DNA Sequences - Rolling Hash, Bit Encoding
October 2025
- 636. Exclusive Time of Functions - Stack, Log Parsing
- 708. Insert into a Sorted Circular Linked List - Two Pointers, Circular List
- 863. All Nodes Distance K in Binary Tree - Graph Conversion, DFS, Parent Pointer
- 1249. Minimum Remove to Make Valid Parentheses - Stack Validation, Parentheses
- 426. Convert Binary Search Tree to Sorted Doubly Linked List - Inorder Traversal, Recursion
- 1094. Car Pooling - Bucket Sort, Event Processing
- 1207. Unique Number of Occurrences - Hash Map, Hash Set
- 348. Design Tic-Tac-Toe - Counter Optimization, State Tracking
- 419. Battleships in a Board - Top-Left Corner, DFS
- 545. Boundary of Binary Tree - DFS, Boundary Traversal
- 347. Top K Frequent Elements - Bucket Sort, Quickselect, Heap
- 973. K Closest Points to Origin - Sorting, Heap, Quickselect
- 207. Course Schedule - Topological Sort, Cycle Detection
- 133. Clone Graph - DFS, BFS, Deep Copy
- 752. Open the Lock - BFS, Shortest Path
- 314. Binary Tree Vertical Order Traversal - BFS, Vertical Order
- 322. Coin Change - DP, Unbounded Knapsack
- 77. Combinations - Backtracking, DFS
- 47. Permutations II - Backtracking, STL, Duplicates
- 46. Permutations - Backtracking, STL
- 1650. Lowest Common Ancestor of a Binary Tree III - Two Pointers, Tree Traversal
- 2043. Simple Bank System - Data Structure Design
- 1443. Minimum Time to Collect All Apples in a Tree - DFS, Tree Traversal
- 84. Largest Rectangle in Histogram - Monotonic Stack
- 695. Max Area of Island - DFS, Connected Components
- 1868. Product of Two Run-Length Encoded Arrays - Two Pointers, Array Processing
- 1865. Finding Pairs With a Certain Sum - Hash Map, Count Tracking
- 1570. Dot Product of Two Sparse Vectors - Hash Map, Optimization
- 437. Path Sum III - DFS, Recursion
- 394. Decode String - Stack, String Processing
- 417. Pacific Atlantic Water Flow - DFS, BFS
- 406. Queue Reconstruction by Height - Greedy, Sorting
Tips for Problem Solving
- Identify the Pattern: Look for common algorithm patterns (DP, sliding window, etc.)
- Start Simple: Begin with brute force, then optimize
- Use Data Structures: Choose appropriate DS for the problem
- Consider Edge Cases: Handle boundary conditions
- Optimize Space/Time: Trade-offs between complexity and efficiency
Last updated: February 27, 2026 Total posts (LC problems): 253