一串数字的平均值

难度等级：新秀
给定数字流，请在每个点上打印该流的平均值(或均值)。例如，让我们将流视为10、20、30、40、50、60，…

Average of 1 numbers is 10.00
  Average of 2 numbers is 15.00
  Average of 3 numbers is 20.00
  Average of 4 numbers is 25.00
  Average of 5 numbers is 30.00
  Average of 6 numbers is 35.00
  ..................

要打印流的均值，我们需要找出如何在向流中添加新数字时求平均值。为此，我们需要的是对流中到目前为止看到的数字，先前的平均值和新数字进行计数。令n为计数， prev_avg为先前的平均值，x为要添加的新数字。包括x个数之后的平均值可以写为(prev_avg * n + x)/(n + 1) 。

C++

#include 
 
// Returns the new average after including x
float getAvg(float prev_avg, int x, int n)
{
    return (prev_avg * n + x) / (n + 1);
}
 
// Prints average of a stream of numbers
void streamAvg(float arr[], int n)
{
    float avg = 0;
    for (int i = 0; i < n; i++) {
        avg = getAvg(avg, arr[i], i);
        printf("Average of %d numbers is %f \n", i + 1, avg);
    }
    return;
}
 
// Driver program to test above functions
int main()
{
    float arr[] = { 10, 20, 30, 40, 50, 60 };
    int n = sizeof(arr) / sizeof(arr[0]);
    streamAvg(arr, n);
 
    return 0;
}

Java

// Java program to find average
// of a stream of numbers
class GFG {
 
    // Returns the new average after including x
    static float getAvg(float prev_avg, float x, int n)
    {
        return (prev_avg * n + x) / (n + 1);
    }
 
    // Prints average of a stream of numbers
    static void streamAvg(float arr[], int n)
    {
        float avg = 0;
        for (int i = 0; i < n; i++)
        {
            avg = getAvg(avg, arr[i], i);
            System.out.printf("Average of %d numbers is %f \n",
                                                   i + 1, avg);
        }
        return;
    }
 
    // Driver program to test above functions
    public static void main(String[] args)
    {
        float arr[] = { 10, 20, 30, 40, 50, 60 };
        int n = arr.length;
        streamAvg(arr, n);
    }
}
 
// This code is contributed by Smitha Dinesh Semwal

Python3

# Returns the new average
# after including x
def getAvg(prev_avg, x, n):
    return ((prev_avg *
             n + x) /
            (n + 1));
 
# Prints average of
# a stream of numbers
def streamAvg(arr, n):
    avg = 0;
    for i in range(n):
        avg = getAvg(avg, arr[i], i);
        print("Average of ", i + 1,
              " numbers is ", avg);
 
# Driver Code
arr = [10, 20, 30,
       40, 50, 60];
n = len(arr);
streamAvg(arr, n);
 
# This code is contributed
# by mits

C#

// C# program to find average
// of a stream of numbers
using System;
 
class GFG
{
 
    // Returns the new average
    // after including x
    static float getAvg(float prev_avg,
                        float x, int n)
    {
        return (prev_avg * n + x) / (n + 1);
    }
 
    // Prints average of
    // a stream of numbers
    static void streamAvg(float[] arr,
                          int n)
    {
        float avg = 0;
        for (int i = 0; i < n; i++)
        {
            avg = getAvg(avg, arr[i], i);
            Console.WriteLine("Average of {0} " +
                                "numbers is {1}",
                                     i + 1, avg);
        }
        return;
    }
 
    // Driver Code
    public static void Main(String[] args)
    {
        float[] arr = {10, 20, 30,
                       40, 50, 60};
        int n = arr.Length;
        streamAvg(arr, n);
    }
}
 
// This code is contributed by mits

Javascript

// javascript program to find average
// of a stream of numbers
 
// Returns the new average after including x
function getAvg( prev_avg,  x,  n)
{
    return (prev_avg * n + x) / (n + 1);
}
 
// Prints average of a stream of numbers
function streamAvg( arr,  n)
{
    let avg = 0;
    for (let i = 0; i < n; i++) {
        avg = getAvg(avg, arr[i], i);
       document.write("Average of "+(i + 1) +" numbers is "+  avg.toFixed(6) + "<br/>");
    }
    return;
}
 
// Driver program to test above functions
    let arr = [10, 20, 30, 40, 50, 60 ];
    let n = arr.length;
    streamAvg(arr, n);
    
// This code is contributed by todaysgaurav
 

---

输出 ：

Average of 1 numbers is 10.000000 
Average of 2 numbers is 15.000000 
Average of 3 numbers is 20.000000 
Average of 4 numbers is 25.000000 
Average of 5 numbers is 30.000000 
Average of 6 numbers is 35.000000 

可以使用以下更改来优化上述函数getAvg()。我们可以通过使用静态变量来避免使用prev_avg和元素数量(假设仅调用此函数来获取流的平均值)。以下是经过优化的版本。

C++

#include 
using namespace std;
 
// Returns the new average after including x
float getAvg(int x)
{
    static int sum, n;
 
    sum += x;
    return (((float)sum) / ++n);
}
 
// Prints average of a stream of numbers
void streamAvg(float arr[], int n)
{
    float avg = 0;
    for (int i = 0; i < n; i++)
    {
        avg = getAvg(arr[i]);
        cout<<"Average of "<

C

#include 
 
// Returns the new average after including x
float getAvg(int x)
{
    static int sum, n;
 
    sum += x;
    return (((float)sum) / ++n);
}
 
// Prints average of a stream of numbers
void streamAvg(float arr[], int n)
{
    float avg = 0;
    for (int i = 0; i < n; i++) {
        avg = getAvg(arr[i]);
        printf("Average of %d numbers is %f \n", i + 1, avg);
    }
    return;
}
 
// Driver program to test above functions
int main()
{
    float arr[] = { 10, 20, 30, 40, 50, 60 };
    int n = sizeof(arr) / sizeof(arr[0]);
    streamAvg(arr, n);
 
    return 0;
}

Java

// Java program to return
// Average of a stream of numbers
class GFG
{
static int sum, n;
     
// Returns the new average
// after including x
static float getAvg(int x)
{
    sum += x;
    return (((float)sum) / ++n);
}
 
// Prints average of a
// stream of numbers
static void streamAvg(float[] arr,
                      int n)
{
    float avg = 0;
    for (int i = 0; i < n; i++)
    {
        avg = getAvg((int)arr[i]);
        System.out.println("Average of "+ (i + 1) +
                           " numbers is " + avg);
    }
    return;
}
 
// Driver Code
public static void main(String[] args)
{
    float[] arr = new float[]{ 10, 20, 30,
                               40, 50, 60 };
    int n = arr.length;
    streamAvg(arr, n);
}
}
 
// This code is contributed by mits

Python3

# Returns the new average
# after including x
def getAvg(x, n, sum):
    sum = sum + x;
    return float(sum) / n;
 
# Prints average of a
# stream of numbers
def streamAvg(arr, n):
    avg = 0;
    sum = 0;
    for i in range(n):
        avg = getAvg(arr[i], i + 1, sum);
        sum = avg * (i + 1);
        print("Average of ", end = "");
        print(i + 1, end = "");
        print(" numbers is ", end = "");
        print(avg);
    return;
 
# Driver Code
arr= [ 10, 20, 30,
       40, 50, 60 ];
n = len(arr);
streamAvg(arr,n);
 
# This code is contributed by mits

C＃

using System;
 
class GFG
{
static int sum, n;
     
// Returns the new average
// after including x
static float getAvg(int x)
{
 
    sum += x;
    return (((float)sum) / ++n);
}
 
// Prints average of a
// stream of numbers
static void streamAvg(float[] arr, int n)
{
    float avg = 0;
    for (int i = 0; i < n; i++)
    {
        avg = getAvg((int)arr[i]);
        Console.WriteLine("Average of {0} numbers " +
                             "is {1}", (i + 1), avg);
    }
    return;
}
 
// Driver Code
static int Main()
{
    float[] arr = new float[]{ 10, 20, 30,
                               40, 50, 60 };
    int n = arr.Length;
    streamAvg(arr, n);
 
    return 0;
}
}
 
// This code is contributed by mits

Java脚本

// javascript program to return
// Average of a stream of numbers
 
    var sum=0, n=0;
 
    // Returns the new average
    // after including x
    function getAvg(x) {
        sum += x;
        n++;
        return (sum / n);
    }
 
    // Prints average of a
    // stream of numbers
    function streamAvg( arr , m) {
        var avg = 0;
        for (i = 0; i < m; i++) {
            avg = getAvg(parseInt(arr[i]));
            document.write("Average of " + (i + 1) + " numbers is " + avg.toFixed(1)+"<br/>");
        }
        return;
    }
 
    // Driver Code
     
        var arr =  [ 10, 20, 30, 40, 50, 60 ];
        var m = arr.length;
        streamAvg(arr, m);
 
// This code is contributed by todaysgaurav

输出：

Average of 1 numbers is 10.0
Average of 2 numbers is 15.0
Average of 3 numbers is 20.0
Average of 4 numbers is 25.0
Average of 5 numbers is 30.0
Average of 6 numbers is 35.0