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 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

 > 1) |             ((\$x & 0b01010101) << 1);  }        // Driver Code     \$x = 4;      echo swapBitsInPair(\$x);     // This code is contributed by mits  ?>

Output:

8

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