# Number formed by the rightmost set bit in N

Given an integer N, the task is to find an integer M formed by taking the rightmost set bit in N i.e. the only set bit in M will be the rightmost set bit in N and the rest of the bits will be unset.
Examples:

Input: N = 7
Output:
7 = 111, the number formed by the last set bit is 001 i.e. 1.
Input: N = 10
Output:
10 = 1010 -> 0010 = 2
Input: N = 16
Output: 16

Approach:

• Store x = n & (n – 1) which will unset the first set bit from the right in n.
• Now, update n = n ^ x to set the changed bit and unset all the others which is the required integer.

Below is the implementation of the above approach:

## C++

 `// C++ implementation of the approach` `#include ` `using` `namespace` `std;`   `// Function to return the integer formed` `// by taking the rightmost set bit in n` `int` `firstSetBit(``int` `n)` `{`   `    ``// n & (n - 1) unsets the first set` `    ``// bit from the right in n` `    ``int` `x = n & (n - 1);`   `    ``// Take xor with the original number` `    ``// The position of the 'changed bit'` `    ``// will be set and rest will be unset` `    ``return` `(n ^ x);` `}`   `// Driver code` `int` `main()` `{` `    ``int` `n = 12;`   `    ``cout << firstSetBit(n);`   `    ``return` `0;` `}`

## Java

 `// Java implementation of the approach` `class` `geeks` `{` `    `  `    ``// Function to return the integer formed ` `    ``// by taking the rightmost set bit in n` `    ``public` `static` `int` `firstSetBit(``int` `n)` `    ``{` `        `  `        ``// n & (n - 1) unsets the first set ` `        ``// bit from the right in n` `        ``int` `x = n & (n-``1``);` `        `  `        ``// Take xor with the original number ` `        ``// The position of the 'changed bit' ` `        ``// will be set and rest will be unset` `        ``return` `(n ^ x);` `    ``}` `    `  `    ``// Driver Code` `    ``public` `static` `void` `main (String[] args) ` `    ``{` `        ``int` `n = ``12``;` `        ``System.out.println(firstSetBit(n));` `    ``}` `}`   `// This code is contributed by` `// sanjeev2552`

## Python3

 `# Python3 implementation of the approach`   `# Function to return the integer formed` `# by taking the rightmost set bit in n` `def` `firstSetBit(n):`   `    ``# n & (n - 1) unsets the first set` `    ``# bit from the right in n` `    ``x ``=` `n & (n ``-` `1``)`   `    ``# Take xor with the original number` `    ``# The position of the 'changed bit'` `    ``# will be set and rest will be unset` `    ``return` `(n ^ x)`   `# Driver code` `n ``=` `12`   `print``(firstSetBit(n))`   `# This code is contributed by mohit kumar 29`

## C#

 `// C# implementation of the approach` `using` `System;`   `class` `geeks` `{` `    `  `    ``// Function to return the integer formed ` `    ``// by taking the rightmost set bit in n` `    ``public` `static` `int` `firstSetBit(``int` `n)` `    ``{` `        `  `        ``// n & (n - 1) unsets the first set ` `        ``// bit from the right in n` `        ``int` `x = n & (n-1);` `        `  `        ``// Take xor with the original number ` `        ``// The position of the 'changed bit' ` `        ``// will be set and rest will be unset` `        ``return` `(n ^ x);` `    ``}` `    `  `    ``// Driver Code` `    ``public` `static` `void` `Main () ` `    ``{` `        ``int` `n = 12;` `        ``Console.WriteLine(firstSetBit(n));` `    ``}` `}`   `// This code is contributed by` `// anuj_67..`

## Javascript

 ``

Output:

`4`

Time Complexity: O(1)

Auxiliary Space: O(1)

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