该程序用于查找系列0、0、2、1、4、2、6、3、8中的第n项，…-yiteyi-C++库

给定一个数字N。任务是编写一个程序，在下面的系列中找到第N项：

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0, 0, 2, 1, 4, 2, 6, 3, 8, 4, 10, 5, 12, 6, 14, 7, 16, 8,…..

例子 :

Input : N = 10Output : 4Input : N = 7Output : 6

推荐：请尝试你的方法 {IDE} 首先，在进入解决方案之前。

仔细观察后，您会发现该系列由两个系列组成：

给定序列中奇数位置的项从0开始按递增顺序形成偶数序列。比如，0,2,4,6，。。
给定序列中偶数位置的项是使用公式（previousTerm/2）从上一项导出的。也就是说，在偶数职位上的任期是他们之前任期的一半。

现在，我们知道，每个奇数定位项形成一个从0开始的偶数序列，每个偶数定位项是前一个奇数定位项的一半。因此，首先检查输入数字N是偶数还是奇数。如果它是奇数，则设置N=（N/2）+1（因为有两个系列并行运行），并使用公式2*（N-1）（N-1，因为系列以0开头）。同样，如果N为偶数，则设置N=N/2，使用前面的公式将答案除以2。以下是上述方法的实施情况：

C++

                         // CPP program to find N-th term                       
                         // in the series                       
                         #include <iostream>                       
                         #include <math.h>                       
                         using                                     namespace                                     std;                       
           
                         // Function to find N-th term                       
                         // in the series                       
                         void                                     findNthTerm(                                     int                                     n)                       
                         {                       
                                                 // If n is even                       
                                                 if                                     (n % 2 == 0) {                       
                                                 n = n / 2;                       
                                                 n = 2 * (n - 1);                       
                                                 cout << n / 2 << endl;                       
                                                 }                       
                                                 // If n is odd                       
                                                 else                                     {                       
                                                 n = (n / 2) + 1;                       
                                                 n = 2 * (n - 1);                       
                                                 cout << n << endl;                       
                                                 }                       
                         }                       
           
                         // Driver code                       
                         int                                     main()                       
                         {                       
                                                 int                                     X = 10;                       
                                                 findNthTerm(X);                       
                                   
                                                 X = 7;                       
                                                 findNthTerm(X);                       
                                   
                                                 return                                     0;                       
                         }                       

JAVA

                         // Java program to find N-th term                       
                         // in the series                       
           
                         // Function to find N-th term                       
                         // in the series                       
                         class                                     GFG                       
                         {                       
                         static                                     void                                     findNthTerm(                                     int                                     n)                       
                         {                       
                                                 // If n is even                       
                                                 if                                     (n %                                     2                                     ==                                     0                                     )                       
                                                 {                       
                                                 n = n /                                     2                                     ;                       
                                                 n =                                     2                                     * (n -                                     1                                     );                       
                                                 System.out.println(n /                                     2                                     );                       
                                                 }                       
                                   
                                                 // If n is odd                       
                                                 else                       
                                                 {                       
                                                 n = (n /                                     2                                     ) +                                     1                                     ;                       
                                                 n =                                     2                                     * (n -                                     1                                     );                       
                                                 System.out.println(n);                       
                                                 }                       
                         }                       
           
                         // Driver code                       
                         public                                     static                                     void                                     main(String args[])                       
                         {                       
                                                 int                                     X =                                     10                                     ;                       
                                                 findNthTerm(X);                       
                                   
                                                 X =                                     7                                     ;                       
                                                 findNthTerm(X);                       
                         }                       
                         }                       
           
                         // This code is contributed by Subhadeep                       

Python 3

                         # Python 3 program to find N-th term                       
                         # in the series                       
                                   
                         # Function to find N-th term                       
                         # in the series                       
                         def                                     findNthTerm(n):                       
                                   
                                                 # If n is even                       
                                                 if                                     (n                                     %                                     2                                     =                                     =                                     0                                     ):                       
                                                 n                                     =                                     n                                     /                                     /                                     2                       
                                                 n                                     =                                     2                                     *                                     (n                                     -                                     1                                     )                       
                                                 print                                     ( n                                     /                                     /                                     2                                     )                       
           
                                                 # If n is odd                       
                                                 else                                     :                       
                                                 n                                     =                                     (n                                     /                                     /                                     2                                     )                                     +                                     1                       
                                                 n                                     =                                     2                                     *                                     (n                                     -                                     1                                     )                       
                                                 print                                     (n)                       
                                   
                         # Driver code                       
                         if                                     __name__                                     =                                     =                                     "__main__"                                     :                       
                                                 X                                     =                                     10                       
                                                 findNthTerm(X);                       
                                   
                                                 X                                     =                                     7                                     ;                       
                                                 findNthTerm(X)                       

C#

                         // C# program to find N-th term                       
                         // in the series                       
                         using                                     System;                       
           
                         // Function to find N-th term                       
                         // in the series                       
                         class                                     GFG                       
                         {                       
                         static                                     void                                     findNthTerm(                                     int                                     n)                       
                         {                       
                                                 // If n is even                       
                                                 if                                     (n % 2 == 0)                       
                                                 {                       
                                                 n = n / 2;                       
                                                 n = 2 * (n - 1);                       
                                                 Console.Write(n / 2);                       
                                                 }                       
                                   
                                                 // If n is odd                       
                                                 else                       
                                                 {                       
                                                 n = (n / 2) + 1;                       
                                                 n = 2 * (n - 1);                       
                                                 Console.Write(n);                       
                                                 }                       
                         }                       
           
                         // Driver code                       
                         public                                     static                                     void                                     Main()                       
                         {                       
                                                 int                                     X = 10;                       
                                                 findNthTerm(X);                       
                                                 Console.Write(                                     ""                                     );                       
                                                 X = 7;                       
                                                 findNthTerm(X);                       
                         }                       
                         }                       
           
                         // This code is contributed                       
                         // by Smitha                       

PHP

                         <?php                       
                         // PHP program to find N-th                       
                         // term in the series                       
           
                         // Function to find N-th                       
                         // term in the series                       
                         function                                     findNthTerm(                                     $n                                     )                       
                         {                       
                                                 // If $n is even                       
                                                 if                                     (                                     $n                                     % 2 == 0)                       
                                                 {                       
                                                 $n                                     =                                     $n                                     / 2;                       
                                                 $n                                     = 2 * (                                     $n                                     - 1);                       
                                                 echo                                     $n                                     / 2 .                                     ""                                     ;                       
                                                 }                       
                                   
                                                 // If $n is odd                       
                                                 else                       
                                                 {                       
                                                 $n                                     = (int)(                                     $n                                     / 2) + 1;                       
                                                 $n                                     = 2 * (                                     $n                                     - 1);                       
                                                 echo                                     $n                                     .                                     ""                                     ;                       
                                                 }                       
                         }                       
           
                         // Driver code                       
                         $X                                     = 10;                       
                         findNthTerm(                                     $X                                     );                       
                                   
                         $X                                     = 7;                       
                         findNthTerm(                                     $X                                     );                       
                                   
                         // This code is contributed                       
                         // by ChitraNayal                       
                         ?>                       

Javascript

                         <script>                       
                         // JavaScript program to find N-th term                       
                         // in the series                       
           
                         // Function to find N-th term                       
                         // in the series                       
                         function                                     findNthTerm(n)                       
                         {                       
                                                 // If n is even                       
                                                 if                                     (n % 2 == 0) {                       
                                                 n = Math.floor(n / 2);                       
                                                 n = 2 * (n - 1);                       
                                                 document.write(Math.floor(n / 2) +                                     "<br>"                                     );                       
                                                 }                       
                                                 // If n is odd                       
                                                 else                                     {                       
                                                 n = Math.floor(n / 2) + 1;                       
                                                 n = 2 * (n - 1);                       
                                                 document.write(n +                                     "<br>"                                     );                       
                                                 }                       
                         }                       
                                   
                         // Driver code                       
           
                                                 let X = 10;                       
                                                 findNthTerm(X);                       
                                   
                                                 X = 7;                       
                                                 findNthTerm(X);                       
                                   
                                   
                         // This code is contributed by Surbhi Tyagi                       
           
                         </script>                       

输出：

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