The 18 Patterns

I've organized these patterns into $4$ categories:

$1.$ Array techniques: Two Pointers, Sliding Window, Binary Search, Prefix Sum

$2.$ Data structure patterns: Hash Map, Stack, Monotonic Stack, Heap, Linked List

$3.$ Recursive patterns: Trees, Graphs (BFS/DFS), Backtracking, Dynamic Programming

$4.$ Specialized patterns: Intervals, Greedy, Bit Manipulation

Each pattern has a 'when to use' trigger. Once you learn these triggers, you'll recognize which pattern fits a new problem within seconds.