Single Number II

Given an integer array `nums` where every element appears three times except for one, which appears exactly once. Find the single element and return it. You must implement a solution with a linear runtime complexity and use only constant extra space. ### Constraints - `1 <= nums.length <= 3 * 10^4` - `-2^31 <= nums[i] <= 2^31 - 1` - Each element in `nums` appears exactly three times except for one element which appears once. ### Input Format A single line containing space-separated integers representing `nums`. ### Output Format Print the unique integer.