Unset least significant K bits of a given number

Given an integer N, the task is to print the number obtained by unsetting the least significant K bits from N.

Examples:

Input: N = 200, K=5
Output: 192
Explanation: 
(200)₁₀ = (11001000)₂ 
Unsetting least significant K(= 5) bits from the above binary representation, the new number obtained is (11000000)₂ = (192)₁₀

Input: N = 730, K = 3
Output: 720

Approach: Follow the steps below to solve the problem:

• The idea is to create a mask of the form 111111100000....
• To create a mask, start from all ones as 1111111111....
• There are two possible options to generate all 1s. Either generate it by flipping all 0s with 1s or by using 2s complement and left shift it by K bits.

 mask = ((~0) << K + 1) or 
mask = (-1 << K + 1) 

• Finally, print the value of K + 1 as it is zero-based indexing from the right to left.

Below is the implementation of the above approach:

720

Time Complexity: O(1)
Auxiliary Space: O(1)