LeetCode — Longest consecutive sequence (Blind Curated 31)

Steven Lu
Dec 10, 2022

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Given an unsorted 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 elements sequence is [1, 2, 3, 4]. Therefore its length is 4.

Example 2:

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

Constraints:

  • 0 <= nums.length <= 105
  • -109 <= nums[i] <= 109

Solution:

Time complexity: O(N)

Space complexity: O(1)

LC — Longest Consecutive Sequence (Blind Curated 31)

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