Longest Consecutive Sequence in O(n) Time

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. ### Input Format - A single line containing space-separated integers representing `nums`. If the array is empty, the line is empty. ### Output Format - Print a single integer representing the length of the longest consecutive elements sequence. ### Constraints - `0 <= nums.length <= 10^5` - `-10^9 <= nums[i] <= 10^9`