[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;

    }

};