Modify a bit at a given position

Given a number n, a position p and a binary value b, we need to change the bit at position p in n to value b.

Examples :

Input : n = 7, p = 2, b = 0
Output : 3
7 is 00000111 after clearing bit at 
2rd position, it becomes 0000011.

Input : n = 7, p = 3, b = 1
Output : 15
7 is 00000111 after setting bit at 
3rd position it becomes 00001111.

Recommended: Please try your approach on {IDE} first, before moving on to the solution.

We first create a mask that has set bit only 
at given position using bit wise shift.
      mask = 1 << position

Then to change value of bit to b, we first
make it 0 using below operation
      value & ~mask

After changing it 0, we change it to b by
doing or of above expression with following
(b << p) & mask, i.e., we return
      (n & ~mask) | ((b << p) & mask)

Below is the implementation of above steps :

C++

// CPP program to modify a bit at position 
// p in n to b. 
#include <bits/stdc++.h> 
using namespace std; 
  
// Returns modified n. 
int modifyBit(int n, int p, int b) 
{ 
    int mask = 1 << p; 
    return (n & ~mask) | ((b << p) & mask); 
} 
  
// Driver code 
int main() 
{ 
    cout << modifyBit(6, 2, 0) << endl; 
    cout << modifyBit(6, 5, 1) << endl; 
    return 0; 
} 

Java

// Java program to modify a bit 
// at position p in n to b. 
import java.io.*; 
  
class GFG  
{ 
      
// Returns modified n. 
public static int modifyBit(int n,  
                            int p,  
                            int b) 
{ 
    int mask = 1 << p; 
    return (n & ~mask) |  
           ((b << p) & mask); 
} 
    // Driver Code 
    public static void main (String[] args) 
    { 
        System.out.println(modifyBit(6, 2, 0)); 
        System.out.println (modifyBit(6, 5, 1)); 
    } 
} 
  
// This code is contributed by m_kit 

Python3

# Python3 program to modify a bit at position 
# p in n to b. 
  
# Returns modified n. 
def modifyBit( n,  p,  b): 
    mask = 1 << p 
    return (n & ~mask) | ((b << p) & mask) 
   
# Driver code 
def main(): 
    print(modifyBit(6, 2, 0)) 
    print(modifyBit(6, 5, 1)) 
      
if __name__ == '__main__': 
    main() 
# This code is contributed by PrinciRaj1992 

C#

// C# program to modify a bit 
// at position p in n to b. 
using System; 
  
class GFG 
{ 
// Returns modified n. 
public static int modifyBit(int n,  
                            int p,  
                            int b) 
{ 
    int mask = 1 << p; 
    return (n & ~mask) |  
           ((b << p) & mask); 
} 
  
    // Driver Code 
    static public void Main () 
    { 
      
        Console.WriteLine(modifyBit(6, 2, 0)); 
        Console.WriteLine(modifyBit(6, 5, 1)); 
    } 
} 
  
// This code is contributed by ajit 

PHP

<?php 
// PHP program to modify a bit 
// at position p in n to b. 
  
// Returns modified n. 
function modifyBit($n, $p, $b) 
{ 
    $mask = 1 << $p; 
    return ($n & ~$mask) |  
           (($b << $p) & $mask); 
} 
  
    // Driver code 
    echo modifyBit(6, 2, 0),"\n"; 
    echo modifyBit(6, 5, 1) ,"\n"; 
      
// This code is contributed by ajit 
?> 

Output :

 2
 38

Time Complexity :O(1)

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

Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.

Don’t stop now and take your learning to the next level. Learn all the important concepts of Data Structures and Algorithms with the help of the most trusted course: DSA Self Paced. Become industry ready at a student-friendly price.

My Personal Notes

Recommended: Please try your approach on {IDE} first, before moving on to the solution.

C++

Java

Python3

C#

PHP

Recommended Posts: