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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