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# How to swap two bits in a given integer?

Given an integer n and two-bit positions p1 and p2 inside it, swap bits at the given positions. The given positions are from the least significant bit (lsb). For example, the position for lsb is 0.
Examples:

Input: n = 28, p1 = 0, p2 = 3
Output: 21
Explanation: 28 in binary is 11100.  If we swap 0’th and 3rd digits, we get 10101 which is 21 in decimal.

Input: n = 20, p1 = 2, p2 = 3
Output: 24

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Method 1:
The idea is to first find the bits, then use XOR based swapping concept, i..e., to swap two numbers ‘x’ and ‘y’, we do x = x ^ y,  y = y ^ x, and x = x ^ y.

Below is the implementation of the above idea

## C++

 `// C++ program to swap bits in an integer``#include``using` `namespace` `std;` `// This function swaps bit at positions p1 and p2 in an integer n``int` `swapBits(unsigned ``int` `n, unsigned ``int` `p1, unsigned ``int` `p2)``{``    ``/* Move p1'th to rightmost side */``    ``unsigned ``int` `bit1 =  (n >> p1) & 1;` `    ``/* Move p2'th to rightmost side */``    ``unsigned ``int` `bit2 =  (n >> p2) & 1;` `    ``/* XOR the two bits */``    ``unsigned ``int` `x = (bit1 ^ bit2);` `    ``/* Put the xor bit back to their original positions */``    ``x = (x << p1) | (x << p2);` `    ``/* XOR 'x' with the original number so that the``       ``two sets are swapped */``    ``unsigned ``int` `result = n ^ x;``}` `/* Driver program to test above function*/``int` `main()``{``    ``int` `res =  swapBits(28, 0, 3);``    ``cout<<``"Result = "``<< res<<``" "``;``    ``return` `0;``}` `// This code is contributed by pratham76.`

## C

 `// C program to swap bits in an integer``#include` `// This function swaps bit at positions p1 and p2 in an integer n``int` `swapBits(unsigned ``int` `n, unsigned ``int` `p1, unsigned ``int` `p2)``{``    ``/* Move p1'th to rightmost side */``    ``unsigned ``int` `bit1 =  (n >> p1) & 1;` `    ``/* Move p2'th to rightmost side */``    ``unsigned ``int` `bit2 =  (n >> p2) & 1;` `    ``/* XOR the two bits */``    ``unsigned ``int` `x = (bit1 ^ bit2);` `    ``/* Put the xor bit back to their original positions */``    ``x = (x << p1) | (x << p2);` `    ``/* XOR 'x' with the original number so that the``       ``two sets are swapped */``    ``unsigned ``int` `result = n ^ x;``}` `/* Driver program to test above function*/``int` `main()``{``    ``int` `res =  swapBits(28, 0, 3);``    ``printf``(``"Result = %d "``, res);``    ``return` `0;``}`

## Java

 `// Java program to swap bits in an integer``import` `java.io.*;` `class` `GFG``{``    ` `// This function swaps bit at``// positions p1 and p2 in an integer n``static` `int` `swapBits( ``int` `n, ``int` `p1, ``int` `p2)``{``    ``/* Move p1'th to rightmost side */``    ``int` `bit1 = (n >> p1) & ``1``;` `    ``/* Move p2'th to rightmost side */``    ``int` `bit2 = (n >> p2) & ``1``;` `    ``/* XOR the two bits */``    ``int` `x = (bit1 ^ bit2);` `    ``/* Put the xor bit back to``    ``their original positions */``    ``x = (x << p1) | (x << p2);` `    ``/* XOR 'x' with the original``    ``number so that the``    ``two sets are swapped */``    ``int` `result = n ^ x;``    ``return` `result;``}` `    ``/* Driver code*/``    ``public` `static` `void` `main (String[] args)``    ``{``        ``int` `res = swapBits(``28``, ``0``, ``3``);``        ``System.out.println (``"Result = "` `+ res);``    ``}``}` `// This code is contributed by ajit..`

## C#

 `// C# program to swap bits in an integer``using` `System;``class` `GFG``{` `  ``// This function swaps bit at``  ``// positions p1 and p2 in an integer n``  ``static` `int` `swapBits( ``int` `n, ``int` `p1, ``int` `p2)``  ``{` `    ``/* Move p1'th to rightmost side */``    ``int` `bit1 = (n >> p1) & 1;` `    ``/* Move p2'th to rightmost side */``    ``int` `bit2 = (n >> p2) & 1;` `    ``/* XOR the two bits */``    ``int` `x = (bit1 ^ bit2);` `    ``/* Put the xor bit back to``    ``their original positions */``    ``x = (x << p1) | (x << p2);` `    ``/* XOR 'x' with the original``    ``number so that the``    ``two sets are swapped */``    ``int` `result = n ^ x;``    ``return` `result;``  ``}` `  ``/* Driver code*/``  ``public` `static` `void` `Main(``string``[] args)``  ``{``    ``int` `res = swapBits(28, 0, 3);``    ``Console.Write(``"Result = "` `+ res);``  ``}``}` `// This code is contributed by rutvik_56.`

## Javascript

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## Python3

 `# Python3 program for the above approach` `# This function swaps bit at positions p1 and p2 in an integer n``def` `swapBits(n, p1, p2):` `    ``# Move p1'th to rightmost side``    ``bit1 ``=` `(n >> p1) & ``1` `    ``# Move p2'th to rightmost side``    ``bit2 ``=` `(n >> p2) & ``1` `    ``# XOR the two bits``    ``x ``=` `(bit1 ^ bit2)` `    ``# Put the xor bit back to their original positions``    ``x ``=` `(x << p1) | (x << p2)` `    ``# XOR 'x' with the original number so that the``    ``# two sets are swapped``    ``result ``=` `n ^ x``    ``return` `result`  `# Driver program to test above function``if` `__name__ ``=``=` `'__main__'``:``    ``res ``=` `swapBits(``28``, ``0``, ``3``)``    ``print``(``"Result = "``, res)` `# This code is contributed by nirajgusain5`

Output

`Result = 21 `

Time Complexity: O(1)
Auxiliary Space: O(1)

## C++

 `//C++ code for swapping given bits of a number``#include``using` `namespace` `std;``int` `swapBits(``int` `n, ``int` `p1, ``int` `p2)``{``   ``//left-shift 1 p1 and p2 times``   ``//and using XOR``  ``if` `(((n & (1 << p1)) >> p1) ^ ((n & (1 << p2)) >> p2))``  ``{``    ``n ^= 1 << p1;``    ``n ^= 1 << p2;``  ``}``  ``return` `n;``}` `//Driver Code``int` `main()``{``    ``cout << ``"Result = "` `<< swapBits(28, 0, 3);``    ``return` `0;``}`

## C

 `//C code for swapping given bits of a number``#include``int` `swapBits(``int` `n, ``int` `p1, ``int` `p2)``{``    ``//left-shift 1 p1 and p2 times``    ``//and using XOR``    ``if` `(((n & (1 << p1)) >> p1) ^ ((n & (1 << p2)) >> p2))``    ``{``      ``n ^= 1 << p1;``      ``n ^= 1 << p2;``    ``}``    ``return` `n;``}` `//Driver Code``int` `main()``{``    ``printf``(``"Result = %d"``, swapBits(28, 0, 3));``    ``return` `0;``}`

## Java

 `// Java code for swapping``// given bits of a number``import` `java.util.*;``class` `Main{``  ` `public` `static` `int` `swapBits(``int` `n,``                           ``int` `p1,``                           ``int` `p2)``{``  ``//left-shift 1 p1 and``  ``// p2 times and using XOR``  ``int` `temp = ((n & (``1` `<< p1)) >> p1) ^ ((n & (``1` `<< p2)) >> p2);``  ``if` `(temp >= ``1``)``  ``{``    ``n ^= ``1` `<< p1;``    ``n ^= ``1` `<< p2;``  ``}``  ``return` `n;``}   ` `// Driver code``public` `static` `void` `main(String[] args)``{``  ``System.out.print(``"Result = "` `+``                   ``swapBits(``28``, ``0``, ``3``));``}``}` `// This code is contributed by divyeshrabadiya07`

## Python

 `# Python code for swapping given bits of a number``def` `swapBits(n, p1, p2):` `  ``# left-shift 1 p1 and p2 times``  ``# and using XOR``    ``if` `((n & (``1` `<< p1)) >> p1) ^ ((n & (``1` `<< p2)) >> p2):``        ``n ^``=` `1` `<< p1``        ``n ^``=` `1` `<< p2``    ``return` `n` `# Driver Code``print``(``"Result ="``,swapBits(``28``, ``0``, ``3``))` `# This code is contributed by rag2127`

## C#

 `// C# code for swapping given bits of a number``using` `System;``class` `GFG {` `    ``static` `int` `swapBits(``int` `n, ``int` `p1, ``int` `p2)``    ``{``        ``// left-shift 1 p1 and p2 times``        ``// and using XOR``    ``int` `temp = ((n & (1 << p1)) >> p1) ^ ((n & (1 << p2)));``    ``if` `(temp >= 1)``    ``{``            ``n ^= 1 << p1;``            ``n ^= 1 << p2;``    ``}``    ``return` `n;``    ``}` `    ``// Driver code``    ``static` `void` `Main()``    ``{``        ``Console.WriteLine(``"Result = "` `+ swapBits(28, 0, 3));``    ``}``}` `// This code is contributed by divyesh072019`

## Javascript

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Output

`Result = 21`

Time Complexity: O(1)
Auxiliary Space: O(1)

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