Description
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.
Examples
Input:
nums = [100,4,200,1,3,2]Output:
4Explanation:
The longest consecutive sequence is [1, 2, 3, 4]. Length = 4.
Input:
nums = [0,3,7,2,5,8,4,6,0,1]Output:
9Explanation:
The longest consecutive sequence is [0,1,2,3,4,5,6,7,8]. Length = 9.
Input:
nums = []Output:
0Explanation:
An empty array contains no elements, so there are no consecutive sequences. The length is 0.
Constraints
- •
0 ≤ nums.length ≤ 10⁵ - •
-10⁹ ≤ nums[i] ≤ 10⁹