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.

全体的な考え方:入力数字に対して逆を取るが、数字の前の0は逆を取らないので、数字の最高位を知って、1と逆を取るテクニックを使う.コードは次のとおりです.

#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);
}