# Swap every two bits in bytes

• Difficulty Level : Medium
• Last Updated : 07 Apr, 2021

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```

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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``?>`

## Javascript

 ``

Output:

`8`

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