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.

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

C++

Java

Python3

C#

PHP

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