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Program to clear K-th bit of a number N

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  • Difficulty Level : Medium
  • Last Updated : 08 Nov, 2021

Given a number N, the task is to clear the K-th bit of this number N. If K-th bit is 1, then clear it to 0 and if it is 0 then leave it unchanged.
Examples: 
 

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

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

 

Approach: 
 

  • Since bitwise AND of any bit with a reset bit results in a reset bit, i.e.
Any bit <bitwise AND> Reset bit = Reset bit

which means,
0 & 0 = 0
1 & 0 = 0
  • So for clearing a bit, performing a bitwise AND 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 clear K-th bit of a number N
 
#include <stdio.h>
 
// Function to clear the kth bit of n
int clearBit(int n, int k)
{
    return (n & (~(1 << (k - 1))));
}
 
// Driver code
int main()
{
    int n = 5, k = 1;
 
    printf("%d\n", clearBit(n, k));
 
    return 0;
}

C++




// C++ program to clear K-th bit of a number N
 
#include <bits/stdc++.h>
using namespace std;
 
// Function to clear the kth bit of n
int clearBit(int n, int k)
{
    return (n & (~(1 << (k - 1))));
}
 
// Driver code
int main()
{
    int n = 5, k = 1;
 
    cout<<clearBit(n, k)<<endl;
 
    return 0;
}
 
// This code is contributed by rutvik_56.

Python3




# Python3 program to clear
# K-th bit of a number N
 
# Function to clear the kth bit of n
def clearBit(n, k):
    return (n & ( ~(1 << (k - 1))))
 
# Driver code
n = 5
k = 1
 
print(clearBit(n, k))
 
# This code is contributed
# by Mohit Kumar

Java




// Java program to clear K-th bit of a number N
class GFG
{
     
    // Function to clear the kth bit of n
    static int clearBit(int n, int k)
    {
        return (n & (~(1 << (k - 1))));
    }
     
    // Driver code
    public static void main (String[] args)
    {
        int n = 5, k = 1;
     
        System.out.println(clearBit(n, k));
    }
}
 
// This code is contributed by AnkitRai01

C#




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

Javascript




<script>
 
// JavaScript program to clear K-th bit of a number N
 
// Function to clear the kth bit of n
function clearBit(n, k)
{
    return (n & (~(1 << (k - 1))));
}
 
// Driver code
var n = 5, k = 1;
document.write( clearBit(n, k));
 
</script>

Output: 

4

 

Time Complexity: O(1)

Auxiliary Space: O(1)


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