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Toggle bits in the given range

  • Difficulty Level : Medium
  • Last Updated : 21 May, 2021

Given a non-negative number n and two values l and r. The problem is to toggle the bits in the range l to r in the binary representation of n, i.e, to toggle bits from the rightmost lth bit to the rightmost rth bit. A toggle operation flips a bit 0 to 1 and a bit 1 to 0.
Constraint: 1 <= l <= r <= number of bits in the binary representation of n.
Examples: 
 

Input : n = 17, l = 2, r = 3
Output : 23
(17)10 = (10001)2
(23)10 = (10111)2
The bits in the range 2 to 3 in the binary
representation of 17 are toggled.

Input : n = 50, l = 2, r = 5
Output : 44

 

Approach: Following are the steps:
 

  1. Calculate num as = ((1 << r) – 1) ^ ((1 << (l-1)) – 1) or as ((1 <<r)-l). This will produce a number num having r number of bits and bits in the range l to r are the only set bits.
  2. Now, perform n = n ^ num. This will toggle the bits in the range l to r in n.

 

C/C++




// C++ implementation to toggle bits in
// the given range
#include <bits/stdc++.h>
using namespace std;

// function to toggle bits in the given range
unsigned int toggleBitsFromLToR(unsigned int n,
                                unsigned int l, unsigned int r)
{
    // calculating a number 'num' having 'r'
    // number of bits and bits in the range l
    // to r are the only set bits
    int num = ((1 << r) - 1) ^ ((1 << (l - 1)) - 1);

    // toggle bits in the range l to r in 'n'
    // and return the number
//Besides this, we can calculate num as: num=(1<<r)-l .
    return (n ^ num);
}

// Driver program to test above
int main()
{
    unsigned int n = 50;
    unsigned int l = 2, r = 5;
    cout << toggleBitsFromLToR(n, l, r);
    return 0;
}

Java




// Java implementation to toggle bits in
// the given range
import java.io.*;
 
class GFG
{
    // Function to toggle bits in the given range
    static int toggleBitsFromLToR(int n, int l, int r)
    {
        // calculating a number 'num' having 'r'
        // number of bits and bits in the range l
        // to r are the only set bits
        int num = ((1 << r) - 1) ^ ((1 << (l - 1)) - 1);
  
        // toggle bits in the range l to r in 'n'
        // and return the number
        //Besides this, we can calculate num as: num=(1<<r)-l .
        return (n ^ num);
    }
     
    // driver program
    public static void main (String[] args)
    {
        int n = 50;
        int l = 2, r = 5;
        System.out.println(toggleBitsFromLToR(n, l, r));
    }
}
 
// Contributed by Pramod Kumar

Python3




# Python implementation
# to toggle bits in
# the given range
 
# function to toggle bits
# in the given range
def toggleBitsFromLToR(n,l,r):
 
    # calculating a number
    # 'num' having 'r'
    # number of bits and
    # bits in the range l
    # to r are the only set bits
    num = ((1 << r) - 1) ^ ((1 << (l - 1)) - 1)
  
    # toggle bits in the
    # range l to r in 'n'
    # Besides this, we can calculate num as: num=(1<<r)-l .
 
    # and return the number
    return (n ^ num)
 
# Driver code
 
n = 50
l = 2
r = 5
 
print(toggleBitsFromLToR(n, l, r))
 
# This code is contributed
# by Anant Agarwal.

C#




// C# implementation to toggle bits
// in the given range
using System;
 
namespace Toggle
{
    public class GFG
    {    
                 
    // Function to toggle bits in the given range
    static int toggleBitsFromLToR(int n, int l, int r)
    {
        // calculating a number 'num' having 'r'
        // number of bits and bits in the range l
        // to r are the only set bits
        int num = ((1 << r) - 1) ^ ((1 << (l - 1)) - 1);
 
        // toggle bits in the range l to r in 'n'
        //Besides this, we can calculate num as: num=(1<<r)-l .
        // and return the number
        return (n ^ num);
    }
     
    // Driver Code
    public static void Main ()
    {
        int n = 50;
        int l = 2, r = 5;
        Console.Write(toggleBitsFromLToR(n, l, r));
    }
    }
}
 
// This code is contributed by Sam007.

PHP




<?php
// PHP implementation
// to toggle bits in
// the given range
 
// function to toggle bits
// in the given range
function toggleBitsFromLToR($n, $l, $r)
{
     
    // calculating a number
    // 'num' having 'r'
    // number of bits and
    // bits in the range l
    // to r are the only
    // set bits
    $num = ((1 << $r) - 1) ^
           ((1 << ($l - 1)) - 1);
 
    // toggle bits in the
    // range l to r in 'n'
    //Besides this, we can calculate num as: $num=(1<<$r)-$l .
    // and return the number
 
    return ($n ^ $num);
}
 
    // Driver Code
    $n = 50;
    $l = 2; $r = 5;
    echo toggleBitsFromLToR($n, $l, $r);
 
// This code is contributed by anuj_67
?>

Javascript




<script>
 
// Javascript implementation to toggle bits in
// the given range
 
// function to toggle bits in the given range
function toggleBitsFromLToR(n, l, r)
{
    // calculating a number 'num' having 'r'
    // number of bits and bits in the range l
    // to r are the only set bits
    var num = ((1 << r) - 1) ^ ((1 << (l - 1)) - 1);
 
    // toggle bits in the range l to r in 'n'
    // and return the number
//Besides this, we can calculate num as: num=(1<<r)-l .
    return (n ^ num);
}
 
// Driver program to test above
var n = 50;
var l = 2, r = 5;
document.write( toggleBitsFromLToR(n, l, r));
 
</script>

Output: 
 

44

This article is contributed by Ayush Jauhari. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
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