https://leetcode.com/problems/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.
Example 1:
Input: nums = [2,2,3,2] Output: 3 Example 2:
Input: nums = [0,1,0,1,0,1,99] Output: 99
Constraints:
1 <= nums.length <= 3 * 104 -2^31 <= nums[i] <= 2^31 - 1
Each element in nums appears exactly three times except for one element which appears once.
Follow up: Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory?