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Program for Mean and median of an unsorted array

Given n size unsorted array, find its mean and median.

Mean of an array = (sum of all elements) /
                   (number of elements)

Median of a sorted array of size n is defined 
as below : 
It is middle element when n is odd and average
of middle two elements when n is even.

Since the array is not sorted here, we sort 
the array first, then apply above formula.

Examples:

Input  : a[] = {1, 3, 4, 2, 6, 5, 8, 7}
Output : Mean = 4.5
         Median = 4.5
Sum of the elements is 1 + 3 + 4 + 2 + 6 + 
5 + 8 + 7 = 36
Mean = 36/8 = 4.5
Since number of elements are even, median
is average of 4th and 5th largest elements.
which means (4 + 5)/2 = 4.5

Input  : a[] = {4, 4, 4, 4, 4}
Output : Mean = 4
         Median = 4 


Below is the code implementation:

C++

// CPP program to find mean and median of 
// an array
#include <bits/stdc++.h>
using namespace std;
  
// Function for calculating mean
double findMean(int a[], int n)
{
    int sum = 0;
    for (int i = 0; i < n; i++) 
        sum += a[i];
      
    return (double)sum/(double)n;
}
  
// Function for calculating median
double findMedian(int a[], int n)
{
    // First we sort the array
    sort(a, a+n);
  
    // check for even case
    if (n % 2 != 0)
       return (double)a[n/2];
      
    return (double)(a[(n-1)/2] + a[n/2])/2.0;
}
  
// Driver program
int main()
{
    int a[] = { 1, 3, 4, 2, 7, 5, 8, 6 };
    int n = sizeof(a)/sizeof(a[0]);
    cout << "Mean = " << findMean(a, n) << endl; 
    cout << "Median = " << findMedian(a, n) << endl; 
    return 0;
}

Java

// Java program to find mean 
// and median of an array
import java.util.*;
  
class GFG
{
    // Function for calculating mean
    public static double findMean(int a[], int n)
    {
        int sum = 0;
        for (int i = 0; i < n; i++) 
            sum += a[i];
      
        return (double)sum / (double)n;
    }
  
    // Function for calculating median
    public static double findMedian(int a[], int n)
    {
        // First we sort the array
        Arrays.sort(a);
  
        // check for even case
        if (n % 2 != 0)
        return (double)a[n / 2];
      
        return (double)(a[(n - 1) / 2] + a[n / 2]) / 2.0;
    }
  
    // Driver program
    public static void main(String args[])
    {
        int a[] = { 1, 3, 4, 2, 7, 5, 8, 6 };
        int n = a.length;
        System.out.println("Mean = " + findMean(a, n)); 
        System.out.println("Median = " + findMedian(a, n)); 
    }
}
  
// This article is contributed by Anshika Goyal.

Python3

# Python3 program to find mean 
# and median of an array
  
# Function for calculating mean
def findMean(a, n):
  
    sum = 0
    for i in range( 0, n):
        sum += a[i]
      
    return float(sum/n)
  
# Function for calculating median
def findMedian(a, n):
  
    # First we sort the array
    sorted(a)
  
    # check for even case
    if n % 2 != 0:
        return float(a[n/2])
      
    return float((a[int((n-1)/2)] +
                  a[int(n/2)])/2.0)
  
# Driver program
a = [ 1, 3, 4, 2, 7, 5, 8, 6 ]
n = len(a)
print("Mean =", findMean(a, n))
print("Median =", findMedian(a, n))
  
# This code is contributed by Smitha Dinesh Semwal

C#

// C# program to find mean 
// and median of an array
using System;
  
class GFG
{
    // Function for 
    // calculating mean
    public static double findMean(int []a, 
                                  int n)
    {
        int sum = 0;
        for (int i = 0; i < n; i++) 
            sum += a[i];
      
        return (double)sum / 
               (double)n;
    }
  
    // Function for 
    // calculating median
    public static double findMedian(int []a,
                                    int n)
    {
        // First we sort
        // the array
        Array.Sort(a);
  
        // check for 
        // even case
        if (n % 2 != 0)
        return (double)a[n / 2];
      
        return (double)(a[(n - 1) / 2] + 
                        a[n / 2]) / 2.0;
    }
  
    // Driver Code
    public static void Main()
    {
        int []a = {1, 3, 4, 2, 
                   7, 5, 8, 6};
        int n = a.Length;
        Console.Write("Mean = "
                       findMean(a, n) + 
                                 " "); 
        Console.Write("Median = "
                       findMedian(a, n) + 
                                   " "); 
    }
}
  
// This code is contributed by Smitha .

PHP

<?php 
// PHP program to find mean 
// and median of an array
  
// Function for calculating mean
function findMean(&$a, $n)
{
    $sum = 0;
    for ($i = 0; $i < $n; $i++) 
        $sum += $a[$i];
      
    return (double)$sum
           (double)$n;
}
  
// Function for 
// calculating median
function findMedian(&$a, $n)
{
    // First we sort the array
    sort($a);
  
    // check for even case
    if ($n % 2 != 0)
    return (double)$a[$n / 2];
      
    return (double)($a[($n - 1) / 2] +
                    $a[$n / 2]) / 2.0;
}
  
// Driver Code
$a = array(1, 3, 4, 2, 
           7, 5, 8, 6);
$n = sizeof($a);
echo "Mean = "
      findMean($a, $n)." "
echo "Median = "
      findMedian($a, $n); 
  
// This code is contributed
// by ChitraNayal
?>


Output:

Mean = 4.5
Median = 4.5

Time Complexity to find mean = O(n)
Time Complexity to find median = O(n Log n) as we need to sort the array first. Note that we can find median in O(n) time using methods discussed here and here.

Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.



This article is attributed to GeeksforGeeks.org

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