给定正整数n 。问题是检查在n的二进制表示中是否仅设置了第一位和最后一位。
例子:
Input : 9
Output : Yes
(9)10 = (1001)2, only the first and
last bits are set.
Input : 15
Output : No
(15)10 = (1111)2, except first and last
there are other bits also which are set.
方法:以下是步骤:
- 如果n == 1,则返回“是”。
- 否则检查n-1是否为2的幂。请参阅此文章。
C++
// C++ to check whether the number has only
// first and last bits set
#include
using namespace std;
// function to check whether 'n'
// is a power of 2 or not
bool powerOfTwo(unsigned int n)
{
return (!(n & n-1));
}
// function to check whether the number has only
// first and last bits set
bool onlyFirstAndLastAreSet(unsigned int n)
{
if (n == 1)
return true;
if (n == 2)
return false;
return powerOfTwo(n-1);
}
// Driver program to test above
int main()
{
unsigned int n = 9;
if (onlyFirstAndLastAreSet(n))
cout << "Yes";
else
cout << "No";
return 0;
}
Java
// Java program to check whether the
// number has only first and last
// bits set
import java.util.*;
class GFG
{
// function to check whether 'n'
// is a power of 2 or not
static boolean powerOfTwo(int n)
{
return ((n & n - 1) == 0);
}
// function to check whether the number has
// only first and last bits set
static boolean onlyFirstAndLastAreSet(int n)
{
if (n == 1)
return true;
return powerOfTwo(n-1);
}
// Driver program to test above
public static void main (String[] args) {
int n = Integer.parseUnsignedInt("9");
if (onlyFirstAndLastAreSet(n))
System.out.println("Yes");
else
System.out.println("No");
}
}
/* This code is contributed by Mr. Somesh Awasthi */
Python3
# Python3 program to check whether number
# has only first and last bits set
# function to check whether 'n'
# is a power of 2 or not
def powerOfTwo (n):
return (not(n & n-1))
# function to check whether number
# has only first and last bits set
def onlyFirstAndLastAreSet (n):
if (n == 1):
return True
return powerOfTwo (n-1)
# Driver program to test above
n = 9
if (onlyFirstAndLastAreSet (n)):
print('Yes')
else:
print('No')
# This code is contributed by Shariq Raza
C#
// C# program to check whether the
// number has only first and last
// bits set
using System;
class GFG {
// function to check whether 'n'
// is a power of 2 or not
static bool powerOfTwo(uint n)
{
return ((n & n - 1) == 0);
}
// function to check whether the number has
// only first and last bits set
static bool onlyFirstAndLastAreSet(uint n)
{
if (n == 1)
return true;
return powerOfTwo(n - 1);
}
// Driver program to test above
public static void Main()
{
uint n = (uint)9;
if (onlyFirstAndLastAreSet(n))
Console.WriteLine("Yes");
else
Console.WriteLine("No");
}
}
// This code is contributed by Sam007
PHP
Javascript
输出:
Yes