Day 19: Longest Consecutive Sequence (LeetCode 128) — HashSet | O(n)

Описание: 🎯 Day 19 of My LeetCode Journey | Longest Consecutive Sequence (LeetCode 128)

In this video, I solve LeetCode Problem #128 — Longest Consecutive Sequence using a HashSet to achieve an optimized O(n) solution.
The goal is to find the length of the longest sequence of consecutive numbers in an unsorted array.

🔗 Problem Link:
https://leetcode.com/problems/longest...

📌 PROBLEM SUMMARY:

Given an array of integers nums, return the length of the longest consecutive elements sequence.
You must write an algorithm that runs in O(n) time.

✅ Example 1:

Input: nums = [100, 4, 200, 1, 3, 2]
Output: 4
Explanation: The longest consecutive sequence is [1, 2, 3, 4].

✅ Example 2:

Input: nums = [0,3,7,2,5,8,4,6,0,1]
Output: 9

💡 KEY CONCEPTS:

✅ HashSet for fast lookup
✅ Consecutive sequence detection
✅ Avoiding repeated scans
✅ Optimal O(n) strategy

📊 COMPLEXITY:

• Time: O(n)
• Space: O(n)

🎓 DIFFICULTY: Medium
🏷️ TOPICS: Hash Table, Array, Set, Greedy

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📚 MY LEETCODE JOURNEY PLAYLIST:
   • Leetcode  

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• GitHub: https://github.com/ashwinikemshetty
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