Master one of the most elegant array problems! In this video, I'll show you how to solve LeetCode Problem #128 - Longest Consecutive Sequence with an optimal O(n) time complexity solution using C++. This medium-level problem is a favorite in technical interviews at top tech companies.
🎯 What You'll Learn
✅ Problem Analysis: Understanding consecutive sequences in unsorted arrays
✅ Multiple Approaches: Brute force → Sorting → Optimal Hash Set solution
✅ C++ Implementation: Clean, efficient code with STL containers
✅ Time Optimization: From O(n³) to O(n) - the key insight!
✅ Hash Set Magic: Why unordered_set is perfect for this problem
✅ Interview Tips: How to approach this problem step by step
🚀 Solution Highlights
Time Complexity: O(n) - single pass through the array
Space Complexity: O(n) - hash set for element lookup
Key Insight: Only start counting from sequence beginnings
