Swap every two bits in bytes

Swap all the pair of bits in a byte. Before swapping: 11-10-11-01 After swapping: 11-01-11-10

Examples:

Input  : 00000010
Output : 00000001

Input  : 00000100
Output : 00001000

Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Approach:
x = ((x & 0b10101010) >> 1) | ((x & 0b01010101) <> 1 extracts the high bit position and shifts it to the low bit position.
Similarly the expression (x & 0b01010101) << 1 extracts the low bit from each pair and shifts it to the high bit position.
The two parts are then combined using bitwise-OR.

x= 00011010
((x & 0b10101010) >> 1) = 00001010 >> 1
                        = 00000101
((x & 0b01010101) << 1) = 00010000 <> 1) | ((x & 0b01010101) << 1) = 00100101

Below is the implementation of the above:
Note: This solution works for only 8 bit.

C++

// C++ program to swap every two bits in a byte. 
#include<bits/stdc++.h> 
using namespace std; 
  
unsigned int swapBitsInPair(unsigned int x) 
{ 
    // Extracting the high bit shift it to lowbit 
    // Extracting the low bit shift it to highbit 
    return ((x & 0b10101010) >> 1) |  
            ((x & 0b01010101) << 1);     
} 
  
/* Driver function to test above function */
int main() 
{ 
    unsigned int x = 4;  
    cout << swapBitsInPair(x);     
    return 0; 
} 

Java

// Java program to swap every  
// two bits in a byte. 
import java.util.*; 
  
class GFG 
{ 
    static int swapBitsInPair( int x) 
    { 
        // Extracting the high bit shift it to lowbit 
        // Extracting the low bit shift it to highbit 
        return ((x & 0b10101010) >> 1) |  
                ((x & 0b01010101) << 1);  
    } 
  
    // Driver Function 
    public static void main(String[] args) 
    { 
    int x = 4;  
    System.out.print(swapBitsInPair(x));  
    } 
} 
  
// This code is contributed by Gitanjali. 

Python3

# Python program to swap every  
# two bits in a byte. 
  
import math 
  
def swapBitsInPair( x): 
  
    # Extracting the high bit shift it to lowbit 
    # Extracting the low bit shift it to highbit 
    return ((x & 0b10101010) >> 1) or ((x & 0b01010101) << 1) 
  
# driver Function 
x = 4;  
print(swapBitsInPair(x))  
  
# This code is contributed by Gitanjali. 

C#

// C# program to swap every two bits in a byte. 
using System; 
  
public class GFG{ 
  
    static uint swapBitsInPair(uint x) 
    { 
        // Extracting the high bit shift it to lowbit 
        // Extracting the low bit shift it to highbit 
        return ((x & 010101010) >> 1) |  
                ((x & 001010101) << 1);  
    } 
      
    // Driver function to test above function  
    static public void Main () { 
          
        uint x = 4;  
          
        Console.WriteLine(swapBitsInPair(x));  
    } 
} 
  
// This code is contributed by vt_m. 

PHP

<?php 
// PHP program to swap every 
// two bits in a byte. 
  
function swapBitsInPair($x) 
{ 
      
    // Extracting the high bit  
    // shift it to lowbit 
    // Extracting the low bit 
    // shift it to highbit 
    return (($x & 0b10101010) >> 1) |  
           (($x & 0b01010101) << 1);  
} 
  
    // Driver Code 
    $x = 4;  
    echo swapBitsInPair($x);  
  
// This code is contributed by mits  
?> 