在给定数组中查找子数组均值的均值
给定一个 n 元素数组，您必须找到数组的平均值，作为所有可能的具有连续元素的 m 长度数组的数组的所有连续 m 元素的平均值。
例子：
Input :arr[] = {3, 5, 1, 8, 9, 4},
m = 4
Output : Mean = 5.16667
Explanation : {3, 5, 1, 8}, {5, 1, 8, 9},
{1, 8, 9, 4} are three set of m-consecu-
tive elements. Mean of mean of sets
is (17/4 + 23/4 + 22/4 )/ 3
Input : arr[] = {9, 4}, m = 1
Output : Mean = 6.5
Explanation : {9}, {4} are two set of
1-consecutive element. Mean of means
of sets is (9 + 4 )/ 2一个简单的解决方案是考虑所有大小为 m 的子数组，计算它们的平均值。最后返回均值。
一个有效的解决方案是使用滑动窗口算法来解决这个问题，我们找到 m 长度窗口的总和，然后将每个窗口的平均值相加为一个值总和。最后，我们将通过将总和除以可能的窗口数得到我们的结果，这也是总和/（n-m + 1）。
C++
// CPP program to find mean of means
#include
using namespace std;
// function to find mean value
float findMean(int arr[], int n, int m)
{
// declare sum and winSum (window sum)
float sum = 0, winSum = 0;
int i = 0;
// find sum for 1st m-length window
for (; i < m; i++)
winSum += arr[i];
sum += (winSum / m);
// iterate over array to find sum
// of all m-length means
for (; i < n; i++) {
winSum = winSum - arr[i - m] + arr[i];
sum += (winSum / m);
}
// mean of means will be sum of means
// divided by no of such means
return (sum / (n - m + 1));
}
// Driver code
int main()
{
int arr[] = { 2, 5, 7, 1, 9, 3, 9 };
int n = sizeof(arr) / sizeof(arr[0]);
int m = 4;
cout << "Mean = " << findMean(arr, n, m);
return 0;
} Java
// Java program to find mean of means
import java.util.*;
import java.lang.*;
public class GeeksforGeeks{
// function to find mean value
public static float findMean(int arr[], int n,
int m){
// declare sum and winSum (window sum)
float sum = 0, winSum = 0;
int i = 0;
// find sum for 1st m-length window
for (; i < m; i++)
winSum += arr[i];
sum += (winSum / m);
// iterate over array to find sum
// of all m-length means
for (; i < n; i++) {
winSum = winSum - arr[i - m] + arr[i];
sum += (winSum / m);
}
// mean of means will be sum of means
// divided by no of such means
return (sum / (n - m + 1));
}
// driver code
public static void main(String argc[]){
int arr[] = { 2, 5, 7, 1, 9, 3, 9 };
int n = 7;
int m = 4;
System.out.println("Mean = " +
findMean(arr, n, m));
}
}
/*This code is contributed by Sagar Shukla.*/Python3
# Python3 program to find mean of means
# function to find mean value
def findMean(arr, n, m) :
# declare sum and winSum (window sum)
sum = float(0)
winSum = float(0)
i = 0
# find sum for 1st m-length window
while (i < m):
winSum = winSum + arr[i]
i = i + 1
sum = sum + (winSum / m);
# iterate over array to find sum
# of all m-length means
while (i < n):
winSum = winSum - arr[i - m] + arr[i]
sum = sum + (winSum / m)
i = i + 1
# mean of means will be sum of means
# divided by no of such means
return (sum / (n - m + 1));
# Driven code
arr = [ 2, 5, 7, 1, 9, 3, 9 ]
n = len(arr)
m = 4
print ("Mean = ", findMean(arr, n, m))
# This code is contributed by "rishabh_jain".C#
// Java program to find mean of means
using System;
public class GeeksforGeeks{
// function to find mean value
public static float findMean(int []arr, int n,
int m)
{
// declare sum and winSum (window sum)
float sum = 0, winSum = 0;
int i = 0;
// find sum for 1st m-length window
for (; i < m; i++)
winSum += arr[i];
sum += (winSum / m);
// iterate over array to find sum
// of all m-length means
for (; i < n; i++) {
winSum = winSum - arr[i - m] + arr[i];
sum += (winSum / m);
}
// mean of means will be sum of means
// divided by no of such means
return (sum / (n - m + 1));
}
// driver code
public static void Main(){
int []arr = { 2, 5, 7, 1, 9, 3, 9 };
int n = 7;
int m = 4;
Console.WriteLine("Mean = " +
findMean(arr, n, m));
}
}
/* This code is contributed by vt_m.*/PHP
Javascript
输出：
Mean = 4.9375