Hard Coding Problems
Practice 39 hard coding problems on Code Arena — each with a live judge, worked examples, and a solution editorial.
- Edit Distance — Hard · Dynamic Programming, Strings
- Coin Change — Hard · Dynamic Programming, Greedy
- Longest Common Subsequence — Hard · Dynamic Programming, Strings
- Longest Increasing Subsequence — Hard · Dynamic Programming, Arrays
- 0/1 Knapsack — Hard · Dynamic Programming
- Subset Sum — Hard · Dynamic Programming
- House Robber — Hard · Dynamic Programming
- Unique Grid Paths — Hard · Dynamic Programming, Combinatorics
- Longest Palindromic Substring — Hard · Strings, Dynamic Programming
- Maximum Product Subarray — Hard · Dynamic Programming, Arrays
- Nth Prime — Hard · Number Theory, Math
- Product of Array Except Self — Hard · Arrays, Prefix Sum
- Minimum Meeting Rooms — Hard · Sorting, Greedy
- Subarrays Summing to K — Hard · Arrays, Prefix Sum, Hashing
- Minimum Subset Difference — Hard · Dynamic Programming
- Count Islands — Hard · Graphs
- Coin Change (Count Ways) — Hard · Dynamic Programming
- Longest Common Substring — Hard · Dynamic Programming, Strings
- Minimum Path Sum — Hard · Dynamic Programming, Matrix
- Word Break — Hard · Dynamic Programming, Strings
- Largest Rectangle in Histogram — Hard · Stack
- N-Queens Count — Hard · Backtracking
- Shortest Grid Path — Hard · Graphs
- K-th Permutation — Hard · Combinatorics, Math
- Equal Subset Partition — Hard · Dynamic Programming
- Trapping Rain Water — Hard · Two Pointers
- Maximal Square — Hard · Dynamic Programming, Matrix
- Sliding Window Maximum — Hard · Queue
- Course Schedule — Hard · Graphs
- Decode Ways — Hard · Dynamic Programming, Strings
- Set Matrix Zeroes — Hard · Matrix
- Longest Valid Parentheses — Hard · Dynamic Programming, Stack, Strings
- Max Area of Island — Hard · Graphs
- Minimum Patrol Guards — Hard · Greedy, Intervals
- Shortest Delivery Tour — Hard · Dynamic Programming, Bitmask
- Balanced Bracket Count — Hard · Dynamic Programming, Combinatorics
- Nim Game — Hard · Game Theory, Bitmask
- Treasure Grid — Hard · Dynamic Programming, Matrix
- Job Sequencing — Hard · Greedy, Sorting