数组的期望值或期望值

任何一组数字的期望值或期望值是它表示的实验重复的长期平均值。例如，轧制六面模具的期望值为3.5，因为在大量轧辊中出现的所有数字的平均值接近3.5。粗略地讲，大数定律指出，随着重复次数接近无穷大，这些值的算术平均值几乎可以肯定地收敛到期望值。期望值也称为期望值，数学期望值，EV或第一时刻。
给定一个数组，任务是计算数组的期望值。

例子 ：

Input : [1.0, 2.0, 3.0, 4.0, 5.0, 6.0]
Output : 3.5

Input :[1.0, 9.0, 6.0, 7.0, 8.0, 12.0]
Output :7.16

下面是实现：

C++

// CPP code to calculate expected 
// value of an array
#include 
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 << "\n";
    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.

输出 ：

Expectation of array E(X) is : 3.5

程序的时间复杂度为O(n) 。

正如我们看到的，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。