C++ program to swap adjacent bits

Algorithm:

1. Create a mask to obtain the 0xAAAAAAAA to extract bits.
2. Obtain the odd bits and shift these to even positions.
3. Either create mask2 (0x55555555) for even bits or right shift the mask to extract it. Obtain the even bits and shift these to odd positions.
4. Combine the shifted values of odd and even bits to obtain the converted number.

Program:

#include <iostream>
using namespace std;

unsigned int swap_odd_even(int num){
	int mask=0xAAAAAAAA;
	//A in hexadecimal is equal to 10 in decimal 
	//and 1010 in binary
	
	unsigned int oddbits = (num&mask);
	//right shift for even bits
	unsigned int evenbits = num&(mask>>1);  
	//can also use 0x55555555 as mask for even bits

	return (oddbits>>1) | (evenbits<<1);
}

int main()
{ 
	int T;  //testcases
	cout<<"Enter total number of elements (test cases): ";	
	cin>>T;
	
	//variable to store the number 
	unsigned int N;   

	for(int i=0;i<T;i++)
	{
		cout<<"Enter number: ";	
		cin>>N;
		cout<<"Original number is : "<<N<<endl;
		cout<<"Converted number is :"<<swap_odd_even(N)<<endl;
	}
	
	return 0;
}

Output

Enter total number of elements (test cases): 2
Enter number: 13
Original number is : 13
Converted number is :14
Enter number: 2
Original number is : 2
Converted number is :1