LeetCode 476. 数字的补数（移位 异或^）

class Solution {
public:
    int findComplement(int num) {
        int n = 1, num_copy = num;
        while(num_copy/2)
        {
        	++n;
        	num_copy /= 2;
        }
        while(n)
        {
        	num ^= (1<<n-1);
        	n--;
        }
        return num;
    }
};