Two Pointers

Two pointers is the first real pattern you will learn, and it is one of the most reusable. The idea is simple: instead of checking every pair of elements with nested loops, you place one pointer at each end of a sorted structure and move them toward each other based on a condition. This brings many O(n²) problems down to O(n). Most problems here require a sorted input, so sorting is often the first step. Mastering this pattern also prepares you for fast and slow pointers, which appear in linked list problems later.