The Two Pointers pattern is one of the most fundamental algorithmic techniques for solving array and string problems efficiently. By replacing quadratic, brute-force nested loops with systematic single-pass or convergent scans, this pattern drastically optimizes runtime complexity from O(N^2) to O(N) or to O(NlogN) if sorting is required.
In this deep dive, we will explore how the pattern works, the exact mathematical justification for using it, when to apply (and avoid) it, the primary design templates, and detailed solution strategies for 18 classic LeetCode problems.
What is the Two Pointers Pattern?
The Two Pointers pattern involves maintaining two references (indices) that scan a linear data structure—such as an array, vector, or string—either simultaneously in opposite directions or in the same direction at varying speeds.
Core Benefits
