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 nd 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++

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// 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;
}

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Java

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// 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

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Python3

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# 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

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C#

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// 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..

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Output:

4


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