Two Pointers and Sliding Window: Core Java Patterns for Coding Interviews

A DEV Community tutorial breaks down two fundamental algorithmic techniques — two pointers and sliding window — commonly encountered in coding interviews. The two-pointer approach uses two index variables to traverse a data structure, either moving toward each other or in the same direction, and works well for sorted arrays and in-place modifications. The sliding window technique operates on contiguous subarrays or substrings, with either a fixed or variable-size window that expands and shrinks based on problem conditions. The article provides Java code examples for both patterns, including finding a pair with a target sum and identifying the longest substring without repeating characters. A practical reference table helps readers decide which technique to apply based on problem keywords such as 'subarray', 'substring', 'pair', or 'sorted array'.