88 hand-picked LeetCode problems across 20 core patterns, sequenced so each set builds on the last. No premium-locked problems — everything here is solvable on a free account.
| Two Sum | Easy | |
| Best Time to Buy and Sell Stock | Easy | |
| Maximum Subarray | Medium | |
| Product of Array Except Self | Medium |
| Valid Palindrome | Easy | |
| Two Sum II — Input Array Is Sorted | Medium | |
| 3Sum | Medium | |
| Container With Most Water | Medium | |
| Sort Colors | Medium |
| Longest Substring Without Repeating Characters | Medium | |
| Longest Repeating Character Replacement | Medium | |
| Permutation in String | Medium | |
| Minimum Window Substring | Hard | |
| Sliding Window Maximum | Hard |
| Binary Search | Easy | |
| Search in Rotated Sorted Array | Medium | |
| Find Minimum in Rotated Sorted Array | Medium | |
| Find First and Last Position of Element in Sorted Array | Medium | |
| Median of Two Sorted Arrays | Hard |
| Single Number | Easy | |
| Number of 1 Bits | Easy | |
| Counting Bits | Easy |
| Sqrt(x) | Easy | |
| Happy Number | Easy | |
| Count Primes | Medium | |
| Pow(x, n) | Medium |
| Valid Parentheses | Easy | |
| Valid Anagram | Easy | |
| Find the Index of the First Occurrence in a String | Easy | |
| Group Anagrams | Medium |
| Reverse Linked List | Easy | |
| Merge Two Sorted Lists | Easy | |
| Linked List Cycle | Easy | |
| Add Two Numbers | Medium | |
| Remove Nth Node From End of List | Medium |
| Next Greater Element I | Easy | |
| Daily Temperatures | Medium | |
| Trapping Rain Water | Hard | |
| Largest Rectangle in Histogram | Hard |
| Merge Intervals | Medium | |
| Insert Interval | Medium | |
| Non-overlapping Intervals | Medium |
| Kth Largest Element in a Stream | Easy | |
| Top K Frequent Elements | Medium | |
| Task Scheduler | Medium | |
| Find Median from Data Stream | Hard | |
| Merge k Sorted Lists | Hard |
| Subsets | Medium | |
| Permutations | Medium | |
| Combination Sum | Medium | |
| Word Search | Medium | |
| N-Queens | Hard |
| Different Ways to Add Parentheses | Medium | |
| Kth Largest Element in an Array | Medium | |
| Sort an Array | Medium |
| Maximum Depth of Binary Tree | Easy | |
| Path Sum | Easy | |
| Number of Islands | Medium | |
| Clone Graph | Medium | |
| Surrounded Regions | Medium |
| Binary Tree Level Order Traversal | Medium | |
| 01 Matrix | Medium | |
| Rotting Oranges | Medium | |
| Word Ladder | Hard |
| Course Schedule | Medium | |
| Is Graph Bipartite? | Medium | |
| Pacific Atlantic Water Flow | Medium | |
| Evaluate Division | Medium | |
| Network Delay Time | Medium |
| Course Schedule II | Medium | |
| Find Eventual Safe States | Medium | |
| Minimum Height Trees | Medium |
| Number of Provinces | Medium | |
| Redundant Connection | Medium | |
| Accounts Merge | Medium |
| Implement Trie (Prefix Tree) | Medium | |
| Design Add and Search Words Data Structure | Medium | |
| Word Search II | Hard |
| Climbing Stairs | Easy | |
| House Robber | Medium | |
| Unique Paths | Medium | |
| Coin Change | Medium | |
| Longest Increasing Subsequence | Medium | |
| Word Break | Medium | |
| Longest Palindromic Substring | Medium | |
| Partition Equal Subset Sum | Medium | |
| Longest Common Subsequence | Medium | |
| Edit Distance | Hard |