Set the ith Bit

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.

Examples:

Input : n = 10, k = 2
Output : 14
10 = 1010
Now, set the 2nd bit from right.
14 = 1110
2nd bit has been set.
 
Input : n = 15, k = 3
Output : 15
3rd bit of 15 is already set.

Approach

The idea is to use bitwise OR operator (|) with the converted binary number by left shifting the number by k times!

Implementation

int setIthBit(int &n, int k) {
    return n = n | (i << k)
}

Dry Run

Let's dry run the above implementation with the given example:

n = 10, k = 2

• Binary representation of 10 is 1010
• Left Shift the number by k times: 1 << 2 = 100
• Perform bitwise OR operation: 1010 | 100

  1010
| 0100
-------
  1110

• Return the result: 14

This sets the kth bit in the binary representation of n.

Complexity Analysis