Set the Kth bit of a given number (original) (raw)

Last Updated : 23 Jul, 2025

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**.

Try It Yourself

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

k)∣k) | k)∣n); } // Driver Code n=10;n = 10; n=10;k = 2; echo "Kth bit set number = ", setKthBit($n, $k); // This code is contributed by m_kit ?>

JavaScript

Output:

Kth bit set number = 14

Time Complexity: O(1)

Auxiliary Space: O(1)