数组的期望值或期望值-yiteyi-C++库

期望值概率中的任何一组数字，都是它所代表的实验重复次数的长期平均值。例如，滚动六面模具的预期值为3.5，因为在极大量的滚动中出现的所有数字的平均值接近3.5。不那么粗略地说，大数定律表明，当重复次数接近无穷大时，这些值的算术平均值几乎肯定会收敛到预期值。预期值也称为预料 , 数学期望 ，EV，或第一刻。给定一个数组，任务是计算 期望值 阵列的一部分。 例如：

null

Input : [1.0, 2.0, 3.0, 4.0, 5.0, 6.0]Output : 3.5Input :[1.0, 9.0, 6.0, 7.0, 8.0, 12.0]Output :7.16

以下是实施情况：

C++

                         // CPP code to calculate expected                       
                         // value of an array                       
                         #include <bits/stdc++.h>                       
                         using                                     namespace                                     std;                       
           
                         // Function to calculate expectation                       
                         float                                     calc_Expectation(                                     float                                     a[],                                     float                                     n)                       
                         {                       
                                                 /*variable prb is for probability                       
                                                 of each element which is same for                       
                                                 each element  */                       
                                                 float                                     prb = (1 / n);                       
                                   
                                                 // calculating expectation overall                       
                                                 float                                     sum = 0;                       
                                                 for                                     (                                     int                                     i = 0; i < n; i++)                       
                                                 sum += a[i] * prb;                       
           
                                                 // returning expectation as sum                       
                                                 return                                     sum;                       
                         }                       
           
                         // Driver program                       
                         int                                     main()                       
                         {                       
                                                 float                                     expect, n = 6.0;                       
                                                 float                                     a[6] = { 1.0, 2.0, 3.0,                       
                                                 4.0, 5.0, 6.0 };                       
                                   
                                                 // Function for calculating expectation                       
                                                 expect = calc_Expectation(a, n);                       
                                   
                                                 // Display expectation of given array                       
                                                 cout <<                                     "Expectation of array E(X) is : "                       
                                                 << expect <<                                     ""                                     ;                       
                                                 return                                     0;                       
                         }                       

JAVA

                         // Java code to calculate expected                       
                         // value of an array                       
                         import                                     java.io.*;                       
           
                         class                                     GFG                       
                         {                       
                                                 // Function to calculate expectation                       
                                                 static                                     float                                     calc_Expectation(                                     float                                     a[],                                     float                                     n)                       
                                                 {                       
                                                 // Variable prb is for probability of each                       
                                                 // element which is same for each element                       
                                                 float                                     prb = (                                     1                                     / n);                       
                                   
                                                 // calculating expectation overall                       
                                                 float                                     sum =                                     0                                     ;                       
                                                 for                                     (                                     int                                     i =                                     0                                     ; i < n; i++)                       
                                                 sum += a[i] * prb;                       
           
                                                 // returning expectation as sum                       
                                                 return                                     sum;                       
                                                 }                       
           
                                                 // Driver program                       
                                                 public                                     static                                     void                                     main(String args[])                       
                                                 {                       
                                                 float                                     expect, n = 6f;                       
                                                 float                                     a[] = { 1f, 2f, 3f,                       
                                                 4f, 5f, 6f };                       
                                   
                                                 // Function for calculating expectation                       
                                                 expect = calc_Expectation(a, n);                       
                                   
                                                 // Display expectation of given array                       
                                                 System.out.println(                                     "Expectation of array E(X) is : "                       
                                                 + expect);                       
                                                 }                       
                         }                       
           
                         // This code is contributed by Anshika Goyal.                       

Python3

                         # python code to calculate expected                       
                         # value of an array                       
           
                         # Function to calculate expectation                       
                         def                                     calc_Expectation(a, n):                       
                                   
                                                 # variable prb is for probability                       
                                                 # of each element which is same for                       
                                                 # each element                       
                                                 prb                                     =                                     1                                     /                                     n                       
                                   
                                                 # calculating expectation overall                       
                                                 sum                                     =                                     0                       
                                                 for                                     i                                     in                                     range                                     (                                     0                                     , n):                       
                                                 sum                                     +                                     =                                     (a[i]                                     *                                     prb)                       
                                   
                                                 # returning expectation as sum                       
                                                 return                                     float                                     (                                     sum                                     )                       
           
           
                         # Driver program                       
                         n                                     =                                     6                                     ;                       
                         a                                     =                                     [                                     1.0                                     ,                                     2.0                                     ,                                     3.0                                     ,                                     4.0                                     ,                                     5.0                                     ,                                     6.0                                     ]                       
           
                         # Function for calculating expectation                       
                         expect                                     =                                     calc_Expectation(a, n)                       
           
                         # Display expectation of given array                       
                         print                                     (                                     "Expectation of array E(X) is : "                                     ,                       
                                                 expect )                       
           
                         # This code is contributed by Sam007                       

C#

                         // C# code to calculate expected                       
                         // value of an array                       
                         using                                     System;                       
           
                         class                                     GFG {                       
                                   
                                                 // Function to calculate expectation                       
                                                 static                                     float                                     calc_Expectation(                                     float                                     []a,                       
                                                 float                                     n)                       
                                                 {                       
                                   
                                                 // Variable prb is for probability                       
                                                 // of each element which is same                       
                                                 // for each element                       
                                                 float                                     prb = (1 / n);                       
                                   
                                                 // calculating expectation overall                       
                                                 float                                     sum = 0;                       
                                   
                                                 for                                     (                                     int                                     i = 0; i < n; i++)                       
                                                 sum += a[i] * prb;                       
           
                                                 // returning expectation as sum                       
                                                 return                                     sum;                       
                                                 }                       
           
                                                 // Driver program                       
                                                 public                                     static                                     void                                     Main()                       
                                                 {                       
                                                 float                                     expect, n = 6f;                       
                                                 float                                     []a = { 1f, 2f, 3f,                       
                                                 4f, 5f, 6f };                       
                                   
                                                 // Function for calculating                       
                                                 // expectation                       
                                                 expect = calc_Expectation(a, n);                       
                                   
                                                 // Display expectation of given                       
                                                 // array                       
                                                 Console.WriteLine(                                     "Expectation"                       
                                                 +                                     " of array E(X) is : "                       
                                                 + expect);                       
                                                 }                       
                         }                       
           
                         // This code is contributed by vt_m.                       

PHP

                         <?php                       
                         // PHP code to calculate expected                       
                         // value of an array                       
           
                         // Function to calculate expectation                       
                         function                                     calc_Expectation(                                     $a                                     ,                                     $n                                     )                       
                         {                       
                                                 /*variable prb is for probability                       
                                                 of each element which is same for                       
                                                 each element */                       
                                                 $prb                                     = (1 /                                     $n                                     );                       
                                   
                                                 // calculating expectation overall                       
                                                 $sum                                     = 0;                       
                                                 for                                     (                                     $i                                     = 0;                                     $i                                     <                                     $n                                     ;                                     $i                                     ++)                       
                                                 $sum                                     +=                                     $a                                     [                                     $i                                     ] *                                     $prb                                     ;                       
           
                                                 // returning expectation as sum                       
                                                 return                                     $sum                                     ;                       
                         }                       
           
                         // Driver Code                       
                         $n                                     = 6.0;                       
                         $a                                     =                                     array                                     (1.0, 2.0, 3.0,                       
                                                 4.0, 5.0, 6.0);                       
           
                         // Function for calculating expectation                       
                         $expect                                     = calc_Expectation(                                     $a                                     ,                                     $n                                     );                       
           
                         // Display expectation of given array                       
                         echo                                     "Expectation of array E(X) is : "                                     .                       
                                                 $expect                                     .                                     ""                                     ;                       
           
                         // This code is contributed by Sam007                       
                         ?>                       

Javascript

                         <script>                       
                         // Javascript code to calculate expected                       
                         // value of an array                       
           
                                                 // Function to calculate expectation                       
                                                 function                                     calc_Expectation(a, n)                       
                                                 {                       
                                                 // Variable prb is for probability of each                       
                                                 // element which is same for each element                       
                                                 let prb = (1 / n);                       
                                   
                                                 // calculating expectation overall                       
                                                 let sum = 0;                       
                                                 for                                     (let i = 0; i < n; i++)                       
                                                 sum += a[i] * prb;                       
                                   
                                                 // returning expectation as sum                       
                                                 return                                     sum;                       
                                                 }                       
                                   
                         // driver function                       
           
                                                 let expect, n = 6;                       
                                                 let a = [ 1, 2, 3,                       
                                                 4, 5, 6 ];                       
                                   
                                                 // Function for calculating expectation                       
                                                 expect = calc_Expectation(a, n);                       
                                   
                                                 // Display expectation of given array                       
                                                 document.write(                                     "Expectation of array E(X) is : "                       
                                                 + expect);                       
           
                         </script>                       

输出：

Expectation of array E(X) is : 3.5

程序的时间复杂度是 O（n） . 正如我们所看到的，期望值实际上是数的平均值，我们也可以简单地计算数组的平均值 . 本文由 希曼舒兰扬 .如果你喜欢GeekSforgek，并想贡献自己的力量，你也可以使用写极客。组织或者把你的文章寄到contribute@geeksforgeeks.org.看到你的文章出现在Geeksforgeks主页上，并帮助其他极客。如果您发现任何不正确的地方，或者您想分享有关上述主题的更多信息，请写下评论。

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