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: 1 
7 = 111, the number formed by the last set bit is 001 i.e. 1.
Input: N = 10 
Output: 2 
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 <bits/stdc++.h>
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

<script>
// JavaScript implementation of the approach

// Function to return the integer formed
// by taking the rightmost set bit in n
function firstSetBit(n)
{

    // n & (n - 1) unsets the first set
    // bit from the right in n
    let 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
    let n = 12;
    document.write(firstSetBit(n));

// This code is contributed by Manoj.
</script>

Output:

4

Time Complexity: O(1)

Auxiliary Space: O(1)