Two Pointers Algorithm: How It Solves Sequence Problems in Linear Time

The Two Pointers pattern is an algorithmic technique that tracks two positions simultaneously within a sequence such as an array, string, or linked list. Instead of using nested loops that result in O(n²) complexity, the method moves two pointers according to defined rules, often reducing time complexity to O(n). The pattern applies to a range of problems including palindrome checks, duplicate removal, cycle detection in linked lists, and finding pairs in sorted arrays. Three common variants exist: opposite-end pointers, same-direction pointers, and fast-slow pointers, each suited to different problem types. A structured approach — defining the sequence, setting pointer positions, writing movement rules in plain English, and tracing examples before coding — helps apply the technique effectively.