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Set the K-th bit of a given number
  • Difficulty Level : Easy
  • Last Updated : 27 Apr, 2021

Given a number n and a value k. From the right, set the kth bit in the binary representation of n. The position of LSB(or last bit) is 0, second last bit is 1 and so on. Also, 0 <= k < x, where x is the number of bits in the binary representation of n.
Examples: 
 

Input : n = 10, k = 2
Output : 14
(10)10 = (1010)2
Now, set the 2nd bit from right.
(14)10 = (1110)2
2nd bit has been set.

Input : n = 15, k = 3
Output : 15
3rd bit of 15 is already set.

 

To set any bit we use bitwise OR | operator. As we already know bitwise OR | operator evaluates each bit of the result to 1 if any of the operand’s corresponding bit is set (1). In-order to set kth bit of a number we need to shift 1 k times to its left and then perform bitwise OR operation with the number and result of left shift performed just before. 
 

                            In general, (1 << k) | n.

 

C++




// C++ implementation to set the kth bit
// of the given number
#include <bits/stdc++.h>
 
using namespace std;
 
// function to set the kth bit
int setKthBit(int n, int k)
{
    // kth bit of n is being set by this operation
    return ((1 << k) | n);
}
 
// Driver program to test above
int main()
{
    int n = 10, k = 2;
    cout << "Kth bit set number = "
         << setKthBit(n, k);
    return 0;
}

Java




// Java implementation to set the kth bit
// of the given number
 
class GFG {
     
// function to set the kth bit
static int setKthBit(int n, int k)
{
    // kth bit of n is being set by this operation
    return ((1 << k) | n);
}
 
// Driver code
public static void main(String arg[])
{
    int n = 10, k = 2;
    System.out.print("Kth bit set number = " +
                             setKthBit(n, k));
}
}
 
// This code is contributed by Anant Agarwal.

Python3




# Python implementation
# to set the kth bit
# of the given number
 
# function to set
# the kth bit
def setKthBit(n,k):
 
    # kth bit of n is being
    # set by this operation
    return ((1 << k) | n)
     
# Driver code
 
n = 10
k = 2
 
print("Kth bit set number = ",
          setKthBit(n, k))
 
# This code is contributed
# by Anant Agarwal.

C#




// C# implementation to set the
// kth bit of the given number
using System;
 
class GFG {
     
// function to set the kth bit
static int setKthBit(int n, int k)
{
    // kth bit of n is being set
    // by this operation
    return ((1 << k) | n);
}
 
// Driver code
public static void Main()
{
    int n = 10, k = 2;
    Console.Write("Kth bit set number = "
                    + setKthBit(n, k));
                    
}
}
 
// This code is contributed by
// Smitha Dinesh Semwal.

PHP




<?php
// PHP implementation to
// set the kth bit of
// the given number
 
// function to set
// the kth bit
function setKthBit($n, $k)
{
    // kth bit of n is being
    // set by this operation
    return ((1 << $k) | $n);
}
 
// Driver Code
$n = 10; $k = 2;
echo "Kth bit set number = ",
           setKthBit($n, $k);
 
// This code is contributed by m_kit
?>

Javascript




<script>
    // Javascript implementation to set the
    // kth bit of the given number
     
    // function to set the kth bit
    function setKthBit(n, k)
    {
        // kth bit of n is being set
        // by this operation
        return ((1 << k) | n);
    }
     
    let n = 10, k = 2;
    document.write("Kth bit set number = " + setKthBit(n, k));
     
    // This code is contributed by rameshtravel07.
</script>

Output: 
 



Kth bit set number = 14

This article is contributed by Ayush Jauhari. 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.
 

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