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Sliding Window

Learn the sliding window technique to efficiently solve array and string problems. Master fixed-size and variable-size window patterns.

The Sliding Window technique transforms $O (N^{2})$ brute force solutions into efficient $O (N)$ algorithms by maintaining a "window" of elements and sliding it through the data structure. Master fixed-size and variable-size windows, learn when to use the pattern, and avoid common pitfalls with our comprehensive guide.

Featured Guide

Complete Guide

Sliding Window: The Complete Guide (Patterns, Templates, and LeetCode Examples)

A senior-engineer-level guide to the sliding window pattern for LeetCode: intuition, templates, examples, debugging checklists, and how it compares to two pointers and prefix sums.

22 min read

Tutorials

When NOT to Use the Sliding Window Technique (5 Patterns Where It Fails)

Sliding Window is a powerful optimization, but it's not a silver bullet. Learn the 5 specific scenarios where this pattern fails and what to use instead to save your interview.

Sliding WindowLeetCode PatternAlgorithm Strategy

8 min

Sliding Window Intuition Explained Step-by-Step (For Beginners)

Struggling to understand when to shrink or expand the window? This step-by-step guide breaks down the intuition behind the Sliding Window pattern with visual examples and mental models.

Sliding WindowAlgorithmsBeginner Guide

10 min

Sliding Window: Substrings vs Subarrays — What’s the Difference?

Confused between substring and subarray problems? Learn the key differences in how Sliding Window applies to strings versus arrays and avoid common implementation pitfalls.

Sliding WindowSubstringSubarray

6 min

Why Your Sliding Window "Shrinks Wrong" — A Debugging Guide

Stuck in an infinite loop? Window expanding too much? Learn the common bugs that cause Sliding Window solutions to fail and how to fix them with a simple debugging checklist.

DebuggingSliding WindowCommon Bugs

8 min

Sliding Window Off-by-One Errors — How to Fix Them

Is the length 'right - left' or 'right - left + 1'? Stop guessing. Learn the definitive logic for calculating window size and handling boundaries correctly.

Sliding WindowOff-by-oneBugs

5 min

Fixed Window vs Dynamic Window: Which Sliding Window Technique to Use?

Not all windows are created equal. Learn the critical difference between Fixed-Size and Dynamic-Size Sliding Windows, and get the decision matrix to choose the right one instantly.

Sliding WindowFixed WindowDynamic Window

7 min

Sliding Window vs Prefix Sum: When to Use Which?

They both solve subarray problems in O(N). But pick the wrong one, and you'll hit a wall. Learn the key differences between Sliding Window and Prefix Sums.

Sliding WindowPrefix SumAlgorithm Comparison

6 min

How to Recognize Sliding Window Problems Instantly (Pattern Triggers)

Stop guessing algorithms. Learn the 4 keywords that scream 'Sliding Window' and the mindset checklist to confirm your intuition in seconds.

Pattern RecognitionInterview TipsSliding Window

5 min

Sliding Window for Negative Numbers — Why It Breaks & What to Do Instead

Why does adding a negative number break your O(N) solution? Understand the math behind the failure and learn the correct alternatives like Prefix Sums.

Negative NumbersEdge CasesPrefix Sum

6 min

Why Sliding Window Doesn’t Work on LeetCode Stock Problems

Best Time to Buy and Sell Stock looks like a window problem. But trying to use Sliding Window will lead you down a rabbit hole. Learn why DP or Greedy is the real answer.

Stock ProblemsDynamic ProgrammingGreedy

6 min

Sliding Window Template Explained (Python / Java / JavaScript)

Master the universal sliding window template across Python, Java, and JavaScript. Learn how to avoid reinventing the wheel and ship bug-free solutions faster in coding interviews.

Sliding WindowLeetCodeInterview Prep

12 min

Common Sliding Window Mistakes (And How to Fix Them)

Knowing sliding window doesn't mean you'll solve it correctly. Learn the 6 most common mistakes that trip up candidates and how to debug them before your interviewer notices.

Sliding WindowDebuggingLeetCode

16 min

Sliding Window vs Two Pointers: Which Technique to Use?

Stop confusing these two patterns. Learn the precise differences between sliding window and two pointers, when to use each, and how they overlap in coding interviews.

Sliding WindowTwo PointersLeetCode

13 min

How to Apply Sliding Window in 2D / Matrix Problems

Sliding window isn't just for arrays—learn how to extend this powerful pattern to 2D matrices and grids. Master dimension compression and avoid common pitfalls in matrix problems.

Sliding Window2D ArrayMatrix

15 min

Sliding Window

Featured Guide

Sliding Window: The Complete Guide (Patterns, Templates, and LeetCode Examples)

Tutorials

When NOT to Use the Sliding Window Technique (5 Patterns Where It Fails)

Sliding Window Intuition Explained Step-by-Step (For Beginners)

Sliding Window: Substrings vs Subarrays — What’s the Difference?

Why Your Sliding Window "Shrinks Wrong" — A Debugging Guide

Sliding Window Off-by-One Errors — How to Fix Them

Fixed Window vs Dynamic Window: Which Sliding Window Technique to Use?

Sliding Window vs Prefix Sum: When to Use Which?

How to Recognize Sliding Window Problems Instantly (Pattern Triggers)

Sliding Window for Negative Numbers — Why It Breaks & What to Do Instead

Why Sliding Window Doesn’t Work on LeetCode Stock Problems

Sliding Window Template Explained (Python / Java / JavaScript)

Top Sliding Window Problems on LeetCode (Ranked by Difficulty)

Common Sliding Window Mistakes (And How to Fix Them)

Sliding Window vs Two Pointers: Which Technique to Use?

How to Apply Sliding Window in 2D / Matrix Problems