Calculate median of the array

Posted on Apr 24, 2020

C program to calculate median of the array.

Median is the middle value of a set of data. To calculate the median first we need to sort the list in ascending or descending order.
  • If the number of elements are even, then the median is the average of two numbers in the middle.
  • If the number of elements are odd then the middle element of the array after sorting will be considered as the median.

    For example,
    Array elements: 2, 5, 4, 3, 1
    Sorted array: 1, 2, 3, 4, 5
    Median: 3.000000 (middle element)

    Array elements: 2, 5, 4, 6, 3, 1
    Sorted array: 1, 2, 3, 4, 5, 6
    Median: 3.500000 ((3 + 4)/2)

    • Program 

    #include<stdio.h>
#include<conio.h>
#define MAX 50

void read_array(int a[MAX], int n)
{
    int i;
    for(i=0;i<n;i++)
    {
        printf("Element %d\t:",i+1);
        scanf("%d",&a[i]);
    }
}

void print_array(int a[MAX], int n)
{
    int i;
    for(i=0;i<n;i++)
    {
        printf("Element %d\t:%d\n",i+1,a[i]);
    }
}

void sort(int a[MAX], int n)
{
    int i, j, temp;
    for(i=0;i<n;i++)
    {
        for(j=i+1;j<n;j++)
        {
            if(a[i] > a[j])
            {
                temp = a[i];
                a[i] = a[j];
                a[j] = temp;
            }
        }
    }
}

float median(int a[MAX], int n)
{
    float med;
    if(n%2 == 0)
    {
        med = (a[(n-1)/2] + a[n/2]) / 2.0;
    }
    else
    {
        med = a[n/2];
    }
    return med;
}

void main()
{
    int arr[MAX];
    int i, j, n, temp;
    float med;

    printf("Enter the number of elements in the array\t:");
    scanf("%d",&n);

    printf("Enter the elements of the array\n");
    read_array(arr, n);

    sort(arr, n);

    printf("\nSorted array\n");
    print_array(arr, n);

    med = median(arr, n);
    printf("\nMedian of the above array is %f",med);

    getch();
}

    Output 

    ********** Run1 ********** 

Enter the number of elements in the array       :7
Enter the elements of the array
Element 1       :12
Element 2       :25
Element 3       :54
Element 4       :89
Element 5       :65
Element 6       :23
Element 7       :57

Sorted array
Element 1       :12
Element 2       :23
Element 3       :25
Element 4       :54
Element 5       :57
Element 6       :65
Element 7       :89

Median of the above array is 54.000000


********** Run2 ********** 

Enter the number of elements in the array       :8
Enter the elements of the array
Element 1       :12
Element 2       :56
Element 3       :45
Element 4       :78
Element 5       :36
Element 6       :59
Element 7       :95
Element 8       :84

Sorted array
Element 1       :12
Element 2       :36
Element 3       :45
Element 4       :56
Element 5       :59
Element 6       :78
Element 7       :84
Element 8       :95

Median of the above array is 57.500000