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🔥Longest Consecutive Sequence: O(n) Streak TrackerMedium
MediumArrays & Hashing•Acceptance: 47.5%

Longest Consecutive Sequence: O(n) Streak Tracker

Real-World Engineering Context
Used by gaming servers and Habit Tracker platforms like Duolingo to detect longest uninterrupted daily activity streaks without sorting.
Given an unsorted array of integers `nums`, return the length of the longest consecutive elements sequence. The algorithm must run in O(n) time.

Sample Test Cases

Input: [[100,4,200,1,3,2]]
Expected: 4
Input: [[0,3,7,2,5,8,4,6,0,1]]
Expected: 9
Input: [[]]
Expected: 0

Constraints

  • 0 <= nums.length <= 10^5
  • -10^9 <= nums[i] <= 10^9