Program for Mean and median of an unsorted array

Given an unsorted array a[] of size N, the task is to find its mean and median. 

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

The median of a sorted array of size N is defined as the 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
Explanation: 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 Median = (4 + 5)/2 = 4.5

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

Approach:  To solve the problem follow the below steps:

To find median:

• First, simply sort the array
• Then, check if the number of elements present in the array is even or odd
• If odd, then simply return the mid value of the array
• Else, the median is the average of the two middle values

To find Mean:

• At first, find the sum of all the numbers present in the array.
• Then, simply divide the resulted sum by the size of the array

Below is the code implementation: 

C

// C program to find mean and median of
// an array
#include <stdio.h>
#include <stdlib.h>

// Function to compare two integers for qsort
int cmpfunc(const void* a, const void* b)
{
    return (*(int*)a - *(int*)b);
}

// 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
    qsort(a, n, sizeof(int), cmpfunc);

    // 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
int main()
{
    int a[] = { 1, 3, 4, 2, 7, 5, 8, 6 };
    int N = sizeof(a) / sizeof(a[0]);

    // Function call
    printf("Mean = %f\n", findMean(a, N));
    printf("Median = %f\n", findMedian(a, N));
    return 0;
}

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 code
int main()
{
    int a[] = { 1, 3, 4, 2, 7, 5, 8, 6 };
    int N = sizeof(a) / sizeof(a[0]);

    // Function call
    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 code
    public static void main(String args[])
    {
        int a[] = { 1, 3, 4, 2, 7, 5, 8, 6 };
        int n = a.length;

        // Function call
        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[int(n/2)])

    return float((a[int((n-1)/2)] +
                  a[int(n/2)])/2.0)


# Driver code
a = [1, 3, 4, 2, 7, 5, 8, 6]
n = len(a)

# Function call
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;

        // Function call
        Console.Write("Mean = " + findMean(a, n) + "\n");
        Console.Write("Median = " + findMedian(a, n)
                      + "\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);

// Function call
echo "Mean = " .
      findMean($a, $n)."\n";
echo "Median = " .
      findMedian($a, $n);

// This code is contributed
// by ChitraNayal
?>

Javascript

<script>

// Javascript program to find mean
// and median of an array

// Function for
// calculating mean
function findMean(a,n)
{
    let sum = 0;
    for (let i = 0; i < n; i++)
        sum += a[i];

    return sum / n;
}

// Function for
// calculating median
function findMedian(a,n)
{
    // First we sort
    // the array
    a.sort();

    // check for
    // even case
    if (n % 2 != 0)
        return a[n / 2];

    return (a[Math.floor((n-1)/2)] +
            a[n / 2]) / 2;
}

// Driver Code

let a = [1, 3, 4, 2, 7, 5, 8, 6]
let n = a.length;

// Function call
document.write("Mean = " + findMean(a, n) + "<br>");
document.write("Median = " + findMedian(a, n));


</script>

Output

Mean = 4.5
Median = 4.5

Complexity Analysis:

Time Complexity to find mean: O(N) 
Time Complexity to find median: O(N Log N) as we need to sort the array first. 
Auxiliary Space: O(1)

This article is contributed by Himanshu Ranjan. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to review-team@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.