Clear the K-th Bit

Given a number n and an integer i, clear the Kth bit of n. Meaning, set the Kth bit of n to 0.

Example

Input: n = 5, K = 2
Output: 1
Explanation: 5 in binary is 101.
Clearing the 2nd bit will result in 001 which is 1 in decimal.

Approach

1. We know how to set the bit k-th position, with the help left shift and OR operator.
2. Now we can do ~(i << k) and then AND it with n to clear the k-th bit.

Code

 
int clearKthBit(int n, int k) {
    return n & (~(1 << k));
}

Dry Run

Let's dry run the code with the given example:

n = 5, K = 2

1. n in binary is 101.
2. 1 << K will be 1 << 2 which is 100.
3. ~(1 << K) will be ~100 which is 011.
   • ~100 is 011 because ~1 is 0 and ~0 is 1 (Not operator).
4. n & (~(1 << K)) will be 101 & 011 which is 001.
5. 001 in decimal is 1.

So, the output is 1.

Complexity Analysis