Single Number II

Given a non-empty array of integers, every element appears three times except for one, which appears exactly once. Find that single one.

Note:

Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory?

Example 1:

Input: [2,2,3,2]
Output: 3

Example 2:

Input: [0,1,0,1,0,1,99]
Output: 99

class Solution {
    public int singleNumber(int[] nums) {
        int answer = 0;
        for (int i = 0; i <= 31; i++) {
            int sum = 0;
            for (int x : nums)
                sum += (x >> i) & 1;
            answer = answer | ((sum % 3) << i);
        }
        return answer;
    }
}