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)10Input: 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:
C++
// C++ program for the above approach#include <bits/stdc++.h>using namespace std;// Function to return the value// after unsetting K LSBsint clearLastBit(int N, int K){ // Create a mask int mask = (-1 << K + 1); // Bitwise AND operation with // the number and the mask return N = N & mask;}// Driver Codeint main(){ // Given N and K int N = 730, K = 3; // Function Call cout << clearLastBit(N, K); return 0;} |
Java
// Java program for the above approachimport java.util.*;class GFG{// Function to return the value// after unsetting K LSBsstatic int clearLastBit(int N, int K){ // Create a mask int mask = (-1 << K + 1); // Bitwise AND operation with // the number and the mask return N = N & mask;}// Driver Codepublic static void main(String[] args){ // Given N and K int N = 730, K = 3; // Function Call System.out.print(clearLastBit(N, K));}}// This code is contributed by shikhasingrajput |
Python3
# Python3 program for the above approach# Function to return the value# after unsetting K LSBsdef clearLastBit(N, K): # Create a mask mask = (-1 << K + 1) # Bitwise AND operation with # the number and the mask N = N & mask return N# Driver Code# Given N and KN = 730K = 3# Function callprint(clearLastBit(N, K))# This code is contributed by Shivam Singh |
C#
// C# program for the above approachusing System;class GFG{// Function to return the value// after unsetting K LSBsstatic int clearLastBit(int N, int K){ // Create a mask int mask = (-1 << K + 1); // Bitwise AND operation with // the number and the mask return N = N & mask;}// Driver Codepublic static void Main(String[] args){ // Given N and K int N = 730, K = 3; // Function Call Console.Write(clearLastBit(N, K));}}// This code is contributed by shikhasingrajput |
Javascript
<script>// javascript program for the above approach// Function to return the value// after unsetting K LSBsfunction clearLastBit(N , K){ // Create a mask var mask = (-1 << K + 1); // Bitwise AND operation with // the number and the mask return N = N & mask;}// Driver Code//Given N and Kvar N = 730, K = 3;// Function Calldocument.write(clearLastBit(N, K));// This code contributed by shikhasingrajput</script> |
720
Time Complexity: O(1)
Auxiliary Space: O(1)
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