single-number-ii leetcode C++

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

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

C++

class Solution {
public:
    int singleNumber(int A[], int n) {
        int res = 0;
        for (int i = 0; i < 32; ++i){
            int sum = 0;
            for (int j = 0;j<n;++j){
                sum += (A[j] >> i) & 1;
            }
            res |= (sum % 3) << i;
        }
        return res;
    }
};