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 least significant bit (lsb). For example, the position for lsb is 0.

Examples:

```Input: n = 28, p1 = 0, p2 = 3
Output: 21
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 ` ` `  `// 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.. `

Python3

 `# Python3 program to swap bits in an integer  ` ` `  `# 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 thetwo sets are swapped '''` `    ``result ``=` `n ^ x ` `    ``return` `result ` `     `  `# Driver Code ` `res ``=` `swapBits(``28``, ``0``, ``3``)  ` `print``(``"Result ="``, res)  ` ` `  `# This code is contributed by SHUBHAMSINGH10 `

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*/` `static` `public` `void` `Main () ` `{ ` `    ``int` `res = swapBits(28, 0, 3); ` `    ``Console.WriteLine(``"Result = "` `+ res); ` `} ` `} ` ` `  `// This code is contributed by akt_mit `

Output:

`Result = 21`

Method 2:
This question can be solved using left shift and XOR operators only. The idea is to set/unset the (p1)th bit and (p2)th bit by left-shifting 1 required number of times and using XOR operator to set/unset that bit (num = num ^ (1 << bit_position)).
Below is the implementation of the above code.

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 ` `    ``n ^= 1 << p1; ` `    ``n ^= 1 << p2; ` `    ``return` `n; ` `} ` ` `  `//Driver Code ` `int` `main() ` `{ ` `    ``cout << ``"Result = "` `<< swapBits(28, 0, 3); ` `    ``return` `0; ` `} ` ` `  `//This code is contributed by yashbeersingh42 `

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 ` `    ``n ^= 1 << p1; ` `    ``n ^= 1 << p2; ` `    ``return` `n; ` `} ` ` `  `//Driver Code ` `int` `main() ` `{ ` `    ``printf``(``"Result = %d"``, swapBits(28, 0, 3)); ` `    ``return` `0; ` `} ` ` `  `//This code is contributed by yashbeersingh42 `

```Output:
Result = 21
```

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