Longest Consecutive Sequence
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
4The longest consecutive elements sequence is
[1, 2, 3, 4], so its length is 4.Example 2
Input
nums = [0,3,7,2,5,8,4,6,0,1]Output
9The longest consecutive elements sequence is
[0, 1, 2, 3, 4, 5, 6, 7, 8], so its length is 9.Constraints
- 0 <= nums.length <= 10^5
- -10^9 <= nums[i] <= 10^9