Set the rightmost unset bit

Difficulty Level : Easy
Last Updated : 05 Apr, 2021

Given a non-negative number n. The problem is to set the rightmost unset bit in the binary representation of n
Examples:

Input : 21
Output : 23
(21)10 = (10101)2
Rightmost unset bit is at position 2(from right) as 
highlighted in the binary representation of 21.
(23)10 = (10111)2
The bit at position 2 has been set.

Input : 2
Output : 3

One method is discussed in this article
This post discusses another method.
Let the input number be n. n+1 would have all the bits flipped after the rightmost unset bit (including the unset bit). So, doing n|(n+1) would give us the required result.

C++

#include <stdio.h>
 
// sets the rightmost unset bit
// of n and returns the result
int fun(unsigned int n)
{
    return n | (n + 1);
}
 
// Driver Code
int main()
{
    int n = 5;
    printf("The number after setting the");
    printf(" rightmost unset bit %d", fun(n));
    return 0;
}

Java

class GFG {
     
    // sets the rightmost unset bit
    // of n and returns the result
    static int fun(int n)
    {
        return n | (n + 1);
    }
     
    // Driver Code
    public static void main(String[] args)
    {
        int n = 5;
        System.out.printf("The number "
                  + "after setting the");
        System.out.printf(" rightmost "
              + " unset bit %d", fun(n));
    }
}
 
// This code is contributed by Smitha

Python3

# sets the rightmost unset bit
# of n and returns the result
def fun(n):
 
    return n | (n + 1)
 
# Driver Code
n = 5
print("The number after setting the", end="")
print(" rightmost unset bit ", fun(n))
 
# This code is contributed by Smitha

C#

using System;
 
class GFG {
     
    // sets the rightmost unset bit
    // of n and returns the result
    static int fun(int n)
    {
        return n | (n + 1);
    }
     
    // Driver Code
    public static void Main()
    {
        int n = 5;
        Console.Write("The number "
            + "after setting the");
        Console.Write(" rightmost "
           + "unset bit "+ fun(n));
    }
}
 
// This code is contributed by Smitha

PHP

<?php
// PHP program to Set the rightmost
// unset bit
 
// sets the rightmost unset bit
// of n and returns the result
function fun($n)
{
    return $n | ($n + 1);
}
 
    // Driver Code
    $n = 5;
    echo "The number after setting the";
    echo " rightmost unset bit ", fun($n);
     
// This code is contributed m_kit
?>

Javascript

<script>
// sets the rightmost unset bit
// of n and returns the result
function fun(n)
{
    return n | (n + 1);
}
 
// Driver Code
    let n = 5;
    document.write("The number after setting the");
    document.write(" rightmost unset bit ", fun(n));
 
// This code is contributed by Manoj.
</script>

Output :

The number after setting the rightmost unset bit 7

Attention reader! Don’t stop learning now. Get hold of all the important DSA concepts with the DSA Self Paced Course at a student-friendly price and become industry ready. To complete your preparation from learning a language to DS Algo and many more, please refer Complete Interview Preparation Course.

In case you wish to attend live classes with industry experts, please refer DSA Live Classes

My Personal Notes

Related Articles

C++

Java

Python3

C#

PHP

Javascript