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Program to toggle K-th bit of a number N

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  • Last Updated : 08 Nov, 2021
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Given a number N, the task is to clear the K-th bit of this number N. If K-th bit is 0, then set it to 1 and if it is 1 then set it to 0.

Examples: 

Input: N = 5, K = 2
Output: 7
5 is represented as 101 in binary
and has its second bit 0, so toggling
it will result in 111 i.e. 7.

Input: N = 5, K = 1
Output: 4
5 is represented as 101 in binary
and has its first bit is 1, so toggling
it will result in 100 i.e. 4.

Approach: 

  • Since XOR of unset and set bit results in a set bit and XOR of a set and set bit results in an unset bit. Hence performing bitwise XOR of any bit with a set bit results in toggle of that bit, i.e.
Any bit <bitwise XOR> Set bit = Toggle

which means,
0 ^ 1 = 1
1 ^ 1 = 0
  • So in order to toggle a bit, performing a bitwise XOR of the number with a reset bit is the best idea.
n = n ^ 1 << k
OR
n ^= 1 << k

where k is the bit that is to be cleared

Below is the implementation of the above approach:  

C++




// C++ program to toggle K-th bit of a number N
#include<bits/stdc++.h>
using namespace std;
 
// Function to toggle the kth bit of n
int toggleBit(int n, int k)
{
    return (n ^ (1 << (k - 1)));
}
 
// Driver code
int main()
{
    int n = 5, k = 2;
    cout << toggleBit(n, k) << endl;
 
    return 0;
}
 
// This code is contributed by noob2000

C




// C program to toggle K-th bit of a number N
 
#include <stdio.h>
 
// Function to toggle the kth bit of n
int toggleBit(int n, int k)
{
    return (n ^ (1 << (k - 1)));
}
 
// Driver code
int main()
{
    int n = 5, k = 2;
 
    printf("%d\n", toggleBit(n, k));
 
    return 0;
}

Java




// Java program to toggle K-th bit of a number N
class GFG
{
 
// Function to toggle the kth bit of n
static int toggleBit(int n, int k)
{
    return (n ^ (1 << (k - 1)));
}
 
// Driver code
public static void main(String []args)
{
    int n = 5, k = 2;
 
    System.out.printf("%d\n", toggleBit(n, k));
}
}
 
// This code is contributed by Rajput-Ji

Python3




# Python3 program to clear K-th bit
# of a number N
 
# Function to toggle the kth bit of n
def toggleBit(n, k) :
 
    return (n ^ (1 << (k - 1)));
 
# Driver code
if __name__ == "__main__" :
 
    n = 5; k = 2;
 
    print(toggleBit(n, k));
 
# This code is contributed by AnkitRai01

C#




// C# program to toggle K-th bit of a number N
using System;
 
class GFG
{
 
// Function to toggle the kth bit of n
static int toggleBit(int n, int k)
{
    return (n ^ (1 << (k - 1)));
}
 
// Driver code
public static void Main(String []args)
{
    int n = 5, k = 2;
 
    Console.WriteLine("{0}", toggleBit(n, k));
}
}
 
// This code is contributed by PrinciRaj1992

Javascript




<script>
 
// Javascript program to toggle K-th bit of a number N
 
// Function to toggle the kth bit of n
function toggleBit(n, k)
{
    return (n ^ (1 << (k - 1)));
}
 
// Driver code
var n = 5, k = 2;
document.write( toggleBit(n, k));
 
// This code is contributed by famously.
</script>

Output: 

7

 

Time Complexity: O(1)

Auxiliary Space: O(1)


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