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
Example 3:
Input: nums = [1,0,1,2]
Output: 3
Constraints:
0 <= nums.length <= 105
-109 <= nums[i] <= 109
Examples
Example 1
Input: [0,3,7,2,5,8,4,6,0,1]
Output: 9
Example 2
Input: [1,0,1,2]
Output: 3
Example 3
Input: [100,4,200,1,3,2]
Output: 4