476. Number Complement

Number Complement
Given a positive integer, output its complement number. The complement strategy is to flip the bits of its binary representation.

Note:
The given integer is guaranteed to fit within the range of a 32-bit signed integer.
You could assume no leading zero bit in the integer’s binary representation.
Example 1:

Input: 5
Output: 2
Explanation: The binary representation of 5 is 101 (no leading zero bits), and its complement is 010. So you need to output 2.

Example 2:

Input: 1
Output: 0
Explanation: The binary representation of 1 is 1 (no leading zero bits), and its complement is 0. So you need to output 0.

总体思路：对输入数字取反，但是数字前面的0不取反，故要知道数字最高位，并用与1亦或取反的技巧。代码如下：

#include
#include
using namespace std;
class Solution {
public:
    int findComplement(int num) {
        int mask = 1, temp = num;
        while (temp>0)
        {
            mask = mask << 1;
            temp = temp >> 1;
        }
        int a=num^(mask - 1);
        cout << a;
        return num^(mask - 1);
    }
};
int main()
{
    Solution n;
    int i;
    cin>>i;
    n.findComplement(i);
}