137.Single Number II

Given an array of integers, every element appears three times except for one. Find that single one.

class Solution {
public:
    int singleNumber(vector<int>& nums) {
        int res = 0;
        for(int i = 0; i < 32; i++){
            int bitSum = 0;
            int bit = 1<<i;
            for(int j = 0; j < nums.size(); j++){
                if(nums[j]&bit){
                    bitSum++;
                }
            }
            if(bitSum % 3 ) res |= bit;
        }
        return res;
    }
};