Two Pointer Technique: A Guide for Coding Interviews

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The two pointer technique is a powerful algorithmic approach that can significantly improve the efficiency of solutions to many coding problems, especially those involving arrays or linked lists. This guide will introduce you to the concept, explain when to use it, and provide examples to help you master this valuable interview skill.

What is the Two Pointer Technique?

The two pointer technique involves using two pointers (or indices) to iterate through a data structure, typically in opposite directions or at different speeds. This approach allows for efficient traversal and comparison of elements, often reducing time complexity from O(n^2) to O(n)[1][2].

When to Use Two Pointers

Consider using the two pointer technique when:

1. Working with sorted arrays or linked lists
2. Searching for pairs or combinations of elements
3. Comparing elements from different positions
4. Detecting cycles or palindromes
5. Partitioning or rearranging elements

Common Two Pointer Patterns

Converging Pointers