[LeetCode]Single Number II

class Solution {
public:
    int singleNumber(int A[], int n) {
        // Note: The Solution object is instantiated only once and is reused by each test case.
        vector<int> bitNum(32, 0);
        for(int i = 0; i < n; ++i)
        {
            for(int j = 0; j < 32; ++j)
            {
                if(A[i] & 1<<j) 
                    bitNum[j]++;
            }
        }
        int res = 0;
        for(int j = 0; j < 32; ++j)
            res += (bitNum[j]%3)<<j;
        return res;
    }
};