Intro

Two pointers uses two indices to traverse a data structure, reducing time complexity from $O(n^2)$ to $O(n)$.

The core insight: Instead of nested loops where the inner loop starts from scratch, move pointers based on the current state. Each pointer moves at most $n$ times, giving $O(n)$ total.

I'll teach you three patterns: opposite direction (converging), same direction (fast and slow), and sorted array pairing. You'll learn when each applies and how to identify two-pointer problems in interviews.