LeetCode--Single Number II

class Solution {
public:
int singleNumber(int A[], int n) {
int a[32] = {0};
int i = 0;
while(i < n)
{
int j = 0;
int num = A[i];
while(j < 32)
{
a[j] += num&1;
num = num>>1;
++j;
}
++i;
}
i = 0;
int ans = 0;
while(i < 32)
{
if(a[i]%3 != 0)
{
ans = ans|(1<<i);
}
++i;
}
return ans;
}
};