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program to find maximum and minimum elements in array using recursion

program to find maximum and minimum elements in array using recursion

Write a C program to find maximum and minimum elements in an array using recursion. How to find maximum and minimum element in an array using recursion in C programming.

Recursion works on the concept of divide and conquer. We break the problem in its smallest size where it can be solved directly. For the maximum/minimum problem, the smallest problem size would be finding maximum/minimum between two elements.

Before writing our main logic, let us first define a recursive function to find maximum element in an array.

int maximum(int array[], int index, int N);

For this recursive approach to find maximum, I have divided the algorithm in three main steps.

    If only two elements are left. We can easily find maximum using array[currentIndex] > array[currentIndex + 1].

    /*
     * This conditions confirms that only two elements 
     * are left i.e. array[index] and array[index + 1]
     */
    if(index == N-2)
    {
        if(array[index] > array[index + 1]) 
        {
            // array[index] i.e. second last element is max
        }
        else
        {
            // array[index + 1] i.e. last element is max
        }
    }

    Find maximum on the right side of current array index. For this step we will use recursive function call.

    max = maximum(array, index + 1, N);

    Finally compare the current array element with maximum element on its right (found in above step).

    if(array[index] > max)
    {
        // array[index] is maximum
    }
    else
    {
        // max is maximum
    }

#include <stdio.h>
#define maxsize 100 // Maximum size of the array

/* Function declarations */
int maximum(int array[], int index, int len);
int minimum(int array[], int index, int len);

int main()
{
    int array[maxsize], N, max, min;
    int i;

    /* Input size and elements of array */
    printf("Enter size of the array: ");
    scanf("%d", &N);
    printf("Enter %d elements in array: ", N);
    for(i=0; i<N; i++)
    {
        scanf("%d", &array[i]);
    }

    max = maximum(array, 0, N);
    min = minimum(array, 0, N);

    printf("Minimum element in array = %d\n", min);
    printf("Maximum element in array = %d\n", max);

    return 0;
}

/* Recursive function to find maximum element in the given array. */
int maximum(int array[], int index, int len)
{
    int max;

    /* Only last and second last element are left     */
    if(index >= len-2)
    {
        if(array[index] > array[index + 1])
            return array[index];
        else
            return array[index + 1];
    }


    /*
     * Recursively call maximum to find maximum element in
     * right side of the array from current index.
     */
    max = maximum(array, index + 1, len);

    /*
     * Compare the current array element with maximum 
     * element on its right side
     */
    if(array[index] > max)
        return array[index];
    else
        return max;
}

/* Recursive function to find minimum element in the array. */
int minimum(int array[], int index, int len)
{
    int min;

    if(index >= len-2)
    {
        if(array[index] < array[index + 1])
            return array[index];
        else
            return array[index + 1];
    }

    min = minimum(array, index + 1, len);

    if(array[index] < min)
        return array[index];
    else
        return min;
}