LeetCode 217: Contains Duplicate | Brute Force vs Set in JavaScript

In this video, I solve LeetCode 217: Contains Duplicate using two different approaches in JavaScript:

1️⃣ A brute force nested loop that checks every pair for duplicates
2️⃣ An optimized approach using a JavaScript Set for constant-time lookups

This is a great beginner-friendly problem to learn how to optimize nested loops into linear-time solutions using hash-based data structures.

I break down both methods, show the code step-by-step, and explain the trade-offs in time and space complexity.

What You’ll Learn:
✅ How to detect duplicates in an array
✅ Why sets make lookup operations fast
✅ How to identify and optimize O(n²) patterns
✅ Time & space complexity comparisons

Chapters:
0:00 - Question
0:55 - Brute Force Code (Nested Loop -O(n*n))
1:40 - Brute Force Explained
3:10 - Optimised Set-Based Explanation
5:07 - Optimised Set-Based Code
5:55 - Summary + Time / Space Complexity for both methods

💬 Want to see this done with sorting (O(n log n) solution)? Let me know in the comments!

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