The complement of an integer is the integer you get when you flip all the `0`'s to `1`'s and all the `1`'s to `0`'s in its binary representation.

- For example, The integer `5` is `"101"` in binary and its complement is `"010"` which is the integer `2`.

Given an integer `num`, return its complement.

Example 1:

    Input: num = 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: num = 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.

Constraints:

- `1 <= num < 231`

Note: This question is the same as 1009: https://leetcode.com/problems/complement-of-base-10-integer/