476. 求二进制的补数 Number Complement

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

Note:

1. The given integer is guaranteed to fit within the range of a 32-bit signed integer.
2. 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.

    public int FindComplement(int num) {
        int number = 0;
        string s = "";
        while (num > 0)
        {
            s = ((num % 2) ^ 1).ToString() + s;
            num /= 2;
        }
        double pow = 0;
        for (int i = s.Length - 1; i >= 0; i--)
        {
            number += (Convert.ToInt32(s[i]) - 48) * (int)Math.Pow(2, pow++);
        }
        return number;
    }

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