给定整数N ,任务是打印通过从N取消设置最低有效K位获得的数字。
例子:
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
方法:请按照以下步骤解决问题:
- 这个想法是创建一个111111100000…形式的蒙版。
- 要创建遮罩,请从1111111111…开始。
- 有两种可能的方法来产生全1。或者通过与1秒翻转所有0秒或通过使用二进制补,并通过K比特左移它生成它。
mask = ((~0) << K + 1) or
mask = (-1 << K + 1)
- 最后,从右到左打印K +1的值,因为它是从零开始的索引。
下面是上述方法的实现:
C++
// C++ program for the above approach
#include
using namespace std;
// Function to return the value
// after unsetting K LSBs
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 Code
int main()
{
// Given N and K
int N = 730, K = 3;
// Function Call
cout << clearLastBit(N, K);
return 0;
}
Java
// Java program for the above approach
import java.util.*;
class GFG{
// Function to return the value
// after unsetting K LSBs
static 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 Code
public 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 LSBs
def 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 K
N = 730
K = 3
# Function call
print(clearLastBit(N, K))
# This code is contributed by Shivam Singh
C#
// C# program for the above approach
using System;
class GFG{
// Function to return the value
// after unsetting K LSBs
static 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 Code
public 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
输出:
720
时间复杂度: O(1)
辅助空间: O(1)