476. Number Complement

Problem:

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

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

思路：

Solution (C++):

int findComplement(int num) {
    unsigned int mask = ~0;

    while (num & mask)  mask <<= 1;
    return mask ^ ~num;
}

性能：

Runtime: 0 ms  Memory Usage: 5.9 MB

思路：

Solution (C++):

性能：

Runtime: ms  Memory Usage: MB