Interview question 05.07 Pairing exchange

Interview questions 05.07. Pairing exchange

Pairing exchange . Programming , Exchange the odd and even digits of an integer , Use as few instructions as possible （ in other words , position 0 And bit 1 In exchange for , position 2 And bit 3 In exchange for , And so on ）.

Example 1:

Input ：num = 2（ perhaps 0b10）
Output 1 ( perhaps 0b01)

Example 2:

Input ：num = 3
Output ：3

This question is actually relatively simple , We need to master some knowledge of bit operation ：
The solution code is as follows , We can keep even bits and odd bits respectively, then move left and right, and then add

int exchangeBits(int num)
{
    
    int a = 0B10101010101010101010101010101010;
    int b = 0B01010101010101010101010101010101;
    a &= num; // Keep odd digits 
    b &= num; // Keep even digits 
    a >>= 1;  // Swap parity bits 
    b <<= 1;
    int ans = a | b;// The odd and even bits can be combined together 
    return ans;
}