Given an unsorted array of integers nums, return the length of the longest consecutive elements sequence.
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 <= 104-109 <= nums[i] <= 109
Follow up: Could you implement the
O(n) solution?