Foundational patterns
- Sliding Window — Maximum Subarray, Longest Substring Without Repeating Characters.
- Two Pointers — Two Sum, Reverse Linked List, Remove Duplicates.
- Hashing — Two Sum, Contains Duplicate, Group Anagrams.
- Greedy — Jump Game, Coin Change, Best Time to Buy/Sell Stock.
- Binary Search — Search Insert Position, Find First/Last Position, Find Peak Element.
Tree, graph, and search
- DFS — Inorder Traversal, Validate BST.
- BFS — Level Order Traversal, Rotting Oranges, Min Depth.
- Graph — Clone Graph, Course Schedule, Number of Islands.
- Trie — Implement Trie, Word Search II, Add and Search Word.
- Topological Sort — Course Schedule, Alien Dictionary.
Dynamic programming family
- Classic DP — Fibonacci, Longest Common Subsequence, Min Path Sum.
- Knapsack — 0/1, Unbounded, Fractional.
- DP + Bitmask — Partition / Subset Sum.
- Memoized recursion — turn brute force into polynomial.
Data-structure-specific
- Stack — Daily Temperatures, RPN.
- Queue — Sliding Window Maximum, Circular Queue.
- Linked List — Reverse, Detect Cycle, Remove Duplicates.
- Matrix — Spiral, Rotate Image, Search 2D Matrix.
- Segment Tree / BIT — Range Sum, Range Min, Range Update.