C Program Count Occurrence of Element in Linked List using Recursion

Recursion : :

• Recursion is the process of repeating items in a self-similar way. In programming languages, if a program allows you to call a function inside the same function, then it is called a recursive call of the function.

• The C programming language supports recursion, i.e., a function to call itself. But while using recursion, programmers need to be careful to define an exit condition from the function, otherwise it will go into an infinite loop.

• Recursive functions are very useful to solve many mathematical problems, such as calculating the factorial of a number, generating Fibonacci series, etc.

Problem : :

This C Program uses recursive function & finds the occurrence for an element in an unsorted list. The user enters the element need to be counted.

Here is the source code of the C Program Count Occurrence of Element in Linked List using Recursion. The C Program is successfully compiled and run on a Linux system. The program output is also shown below.

SOURCE CODE : :

/*  C Program Count Occurrence of Element in Linked List using Recursion  */

#include <stdio.h>

void occur(int [], int, int, int, int *);

int main()
{
    int size, key, count = 0;
    int list[20];
    int i;

    printf("Enter the size of the list: ");
    scanf("%d", &size);
    printf("\nPrinting the list :: \n\n");
    for (i = 0; i < size; i++)
    {
        list[i] = rand() % size;
        printf("%d    ", list[i]);
    }
    printf("\n\nEnter the key to find it's occurrence: ");
    scanf("%d", &key);
    occur(list, size, 0, key, &count);
    printf("\n%d occurs for %d times.\n", key, count);
    return 0;
}

void occur(int list[], int size, int index, int key, int *count)
{
    if (size == index)
    {
        return;
    }
    if (list[index] == key)
    {
        *count += 1;
    }
    occur(list, size, index + 1, key, count);
}

Output : :

/*  C Program Count Occurrence of Element in Linked List using Recursion  */

Enter the size of the list: 8

Printing the list ::

1    3    6    4    1    4    6    6

Enter the key to find it's occurrence: 6

6 occurs for 3 times.

Process returned 0

Above is the source code for C Program Count Occurrence of Element in Linked List using Recursion which is successfully compiled and run on Windows System.The Output of the program is shown above .