[LeetCode] Single Number II

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?

 解题思路，参看http://www.cnblogs.com/changchengxiao/p/3413294.html

class Solution {
public:
    int singleNumber(int A[], int n) {
        // IMPORTANT: Please reset any member data you declared, as
        // the same Solution instance will be reused for each test case.
        int sum[32], ans = 0;
        for(int i = 0;i < 32;i++)
        {
            sum[i] = 0;
            for(int j = 0;j < n;j++)
                if((A[j] >> i) & 1 == 1) 
                    sum[i] = (1 + sum[i]) % 3;
            
            ans = ans | (sum[i] << i);
        }
        return ans;
    }
};