Longest Consecutive Sequence
MediumArray
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