文章作者：Tyan 部落格：noahsnail.com  |  CSDN  |  簡書

1. Description

2. Solution

• Version 1

class Solution {
public:
    int findComplement(int num) {
        int result = 0;
        stack<int> s;
        while(num) {
            int bit = num & 1;
            num >>= 1;
            s.push(bit);
        }
        while
 
(!s.empty()) {
            result <<= 1;
            int bit = s.top();
            s.pop();
            result |= (bit ^ 1);
        }
        return result;
    }
};

• Version 2

class Solution {
public:
    int findComplement(int num) {
        int mask = ~0;
        while (num & mask) {
            mask <<= 1
 
;
        }
        return ~mask & ~num;
    }
};

Reference