Toggle k-th bit

For a given number n, if k-th bit is 0, then toggle it to 1 and if it is 1 then, toggle it to 0.

Examples :

Input : n = 5, k = 1
Output : 4
5 is represented as 101 in binary
and has its first bit 1, so toggling
it will result in 100 i.e. 4.
 
Input : n = 2, k = 3
Output : 6
 
Input : n = 75, k = 4
Output : 67

Approach

1. We know how to convert number into binary.
2. Now inorder to toggle k-th bit, we need to left shift the number 1 by k bits and then XOR it with N

Implementation

int toggleKthBit(int N, int k) {
    return ( N ^ (1 << K)); // XOR with 1 left shifted by k bits
}

Confused? Let's dry run the above code with an example.

Dry Run

Example 1:

Given N = 13, k = 2

N = 13 = 1101
1 << k = 1 << 2 =  100

Now, we will XOR the above two values

👇
1101
0100
-----
1001

Example 2:

Given N = 13, k = 1.

N = 13 = 1101
1 << k = 1 << 1 =  10

  1101
^ 0010
-------
  1111

The output is 14.

If you are not comfortable in XOR XOR Operator.

Complexity Analysis