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.
Input: N = 200, K=5
(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
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:
Time Complexity: O(1)
Auxiliary Space: O(1)