[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;
}
};