LeetCode--Single Number II

思路：

统计每位出现的次数，mod3；对于k同样适用

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;
    }
};