12. Number Complement

Title：

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.

Analysis of Title：

Flip the bits of its binary representation.

Python：

return num^(2**(len(bin(num))-2)-1)

Analysis of Code：

Let‘s solve it down to up.

return b1 ^ b1

return b10  ^ b11

return b11 ^ b11

...

So

...

return num ^ 1,3,7....2**len(num)-1

Notice : When I first to solve it, I want to num ^ 1,11,111,1111....

But actually num is bin and 1,11,... is dec.

12. Number Complement

原文：https://www.cnblogs.com/sxuer/p/10664113.html