Set the K-th bit of a given number

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

Time Complexity: O(1)

Auxiliary Space: O(1)