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Toggle the last m bits
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Toggle the last m bits

Last Updated : 31 May, 2022
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Given a non-negative number n. The problem is to toggle the last m bits in the binary representation of n. A toggle operation flips a bit from 0 to 1 and a bit from 1 to 0.
Constraint: 1 <= m <= n.


Examples: 

Input : n = 21, m = 2 Output : 22 (21)10 = (10101)2 (22)10 = (10110)2 The last two bits in the binary representation of 21 are toggled.  Input : n = 107, m = 4 Output : 100 

Approach: Following are the steps: 

  1. Calculate num = (1 << m) - 1. This will produce a number num having m bits and all will be set.
  2. Now, perform n = n ^ num. This will toggle the last m bits in n.
C++
// C++ implementation to // toggle the last m bits #include <bits/stdc++.h> using namespace std;  // function to toggle // the last m bits unsigned int toggleLastMBits          (unsigned int n, unsigned int m) {          // calculating a number      // 'num' having 'm' bits     // and all are set.      unsigned int num = (1 << m) - 1;      // toggle the last m bits     // and return the number     return (n ^ num); }  // Driver code int main() {     unsigned int n = 107;     unsigned int m = 4;     cout << toggleLastMBits(n, m);     return 0; } 
Java
// Java implementation to // toggle the last m bits import java.util.*; import java.lang.*;  public class GfG{          // function to toggle     // the last m bits     public static int toggleLastMBits                       (int n, int m)     {                  // calculating a number          // 'num' having 'm' bits         // and all are set         int num = (1 << m) - 1;           // toggle the last m bits         // and return the number         return (n ^ num);     }          // Driver function     public static void main(String argc[]){         int n = 107;         int m = 4;         n =  toggleLastMBits(n, m);         System.out.println(n);                    } }  // This code is contributed by Sagar Shukla. 
Python3
# Python implementation to # toggle the last m bits  # function to toggle # the last m bits def toggleLastMBits(n,m):      # calculating a number      # 'num' having 'm' bits     # and all are set.      num = (1 << m) - 1       # toggle the last m bits     # and return the number     return (n ^ num)  # Driver code  n = 107 m = 4 print(toggleLastMBits(n, m))  # This code is contributed # by Anant Agarwal. 
C#
// C# implementation to // toggle the last m bits using System;  namespace Toggle {     public class GFG     {                           // Function to toggle the last m bits     public static int toggleLastMBits(int n, int m)     {                  // Calculating a number 'num' having         // 'm' bits and all are set         int num = (1 << m) - 1;          // Toggle the last m bits         // and return the number         return (n ^ num);     }          // Driver Code     public static void Main() {                  int n = 107, m = 4;         n = toggleLastMBits(n, m);         Console.Write(n);                      }     } }  // This code is contributed by Sam007. 
PHP
<?php // PHP implementation to // toggle the last m bits      // function to toggle     // the last m bits     function toggleLastMBits($n, $m)     {                  // calculating a number          // 'num' having 'm' bits         // and all are set.          $num = (1 << $m) - 1;              // toggle the last m bits         // and return the number         return ($n ^ $num);     }  // Driver code {     $n = 107;     $m = 4;     echo toggleLastMBits($n, $m);     return 0; }  // This code is contributed by nitin mittal. ?> 
JavaScript
<script>  // Javascript implementation to // toggle the last m bits  // function to toggle // the last m bits function toggleLastMBits(n, m) {          // calculating a number      // 'num' having 'm' bits     // and all are set.      var num = (1 << m) - 1;      // toggle the last m bits     // and return the number     return (n ^ num); }  // Driver code var  n = 107; var  m = 4; document.write( toggleLastMBits(n, m));  </script> 

Output: 

100

Time Complexity : O(1)

Auxiliary Space: O(1)

 


Next Article
Toggle the last m bits

A

Ayush
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Article Tags :
  • Bit Magic
  • DSA
Practice Tags :
  • Bit Magic

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