检查数字是否只设置了第一位和最后一位-yiteyi-C++库

给定一个正整数 N .问题是检查在二进制表示中是否只设置了第一位和最后一位 N . 例如：

null

Input : 9Output : Yes(9)₁₀ = (1001)₂, only the first andlast bits are set.Input : 15Output : No(15)₁₀ = (1111)₂, except first and lastthere are other bits also which are set.

建议：请在“上解决” 实践 “首先，在讨论解决方案之前。

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。参考这邮递

C++

                         // C++ to check whether the number has only                       
                         // first and last bits set                       
                         #include <bits/stdc++.h>                       
           
                         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

                         <?php                       
                         // PHP to check whether the number                       
                         // has only first and last bits set                       
           
                         // function to check whether 'n'                       
                         // is a power of 2 or not                       
                         function                                     powerOfTwo(                                     $n                                     )                       
                         {                       
                                                 return                                     (!(                                     $n                                     &                                     $n                                     - 1));                       
                         }                       
           
                         // function to check whether                       
                         // the number has only first                       
                         // and last bits set                       
                         function                                     onlyFirstAndLastAreSet(                                     $n                                     )                       
                         {                       
                                                 if                                     (                                     $n                                     == 1)                       
                                                 return                                     true;                       
                                                 if                                     (                                     $n                                     == 2)                       
                                                 return                                     false;                       
                                                 return                                     powerOfTwo(                                     $n                                     - 1);                       
                         }                       
           
                         // Driver Code                       
                         $n                                     = 9;                       
           
                         if                                     (onlyFirstAndLastAreSet(                                     $n                                     ))                       
                                                 echo                                     "Yes"                                     ;                       
                         else                       
                                                 echo                                     "No"                                     ;                       
           
                         // This code is contributed                       
                         // by Sach_Code                       
                         ?>                       

Javascript

                         <script>                       
           
                         // Javascript to check whether the number has only                       
                         // first and last bits set                       
           
                         // function to check whether 'n'                       
                         // is a power of 2 or not                       
                         function                                     powerOfTwo(n)                       
                         {                       
                                                 return                                     (!(n & n-1));                       
                         }                       
           
                         // function to check whether the number has only                       
                         // first and last bits set                       
                         function                                     onlyFirstAndLastAreSet(n)                       
                         {                       
                                                 if                                     (n == 1)                       
                                                 return                                     true                                     ;                       
                                                 if                                     (n == 2)                       
                                                 return                                     false                                     ;                       
                                                 return                                     powerOfTwo(n-1);                       
                         }                       
           
                         // Driver program to test above                       
                         var                                     n = 9;                       
           
                         if                                     (onlyFirstAndLastAreSet(n))                       
                                                 document.write(                                     "Yes"                                     );                       
                         else                       
                                                 document.write(                                     "No"                                     );                       
                                   
                         </script>                       

输出：

Yes

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