# Count the number of occurrences of an element in a linked list using recursion

In this tutorial, we will learn how to count the number of occurrences of an element in a linked list using recursion using the C program? By Piyas Mukherjee Last updated : August 01, 2023

## Solution

Required function:

```func_occurence ( node *temp) //recursive function
```

## Input

A singly linked list whose address of the first node is stored in a pointer, say head and key is the data of which we have to count the number of occurrences.

## Output

The number of times key occurred in the list, (c)

## Data Structure Used

Singly linked list where each node contains a data element say data and the address of the immediate next node say next, with Head holding the address of the first node.

## Pseudo Code

```Begin
c=0 //global variable
if(temp=NULL)
print c
Else
if(temp->data=key)
c=c+1;
func_occurence(temp->next);
End If
End If-else
End
```

## C program to count the number of occurrences of an element in a linked list using recursion

```#include <stdio.h>
#include <stdlib.h>

typedef struct list {
int data;
struct list* next;
} node;

// global variables
int key, c = 0;
int occurence(node* temp); //function to check occurence

int main()
{
node *head = NULL, *temp, *temp1;
int choice, count;

do {
temp = (node*)malloc(sizeof(node));
if (temp != NULL) {
printf("\nEnter the element in the list : ");
scanf("%d", &temp->data);
temp->next = NULL;
}
else {
while (temp1->next != NULL) {
temp1 = temp1->next;
}
temp1->next = temp;
}
}
else {
printf("\nMemory not avilable...node allocation is not possible");
}
printf("\nIf you wish to add more data on the list enter 1 : ");
scanf("%d", &choice);
} while (choice == 1);

printf("\nEnter the data to find it's occurrence : ");
scanf("%d", &key);
printf("%d occured %d times in the list", key, count);

return 0;
}

//finding occurence of the key value
int occurence(node* temp)
{
if (temp == NULL)
return c;
else {
if (temp->data == key)
c = c + 1;
occurence(temp->next);
}
}
```

## Output

```Enter the element in the list : 1

If you wish to add more data on the list enter 1 : 1

Enter the element in the list : 2

If you wish to add more data on the list enter 1 : 1

Enter the element in the list : 3

If you wish to add more data on the list enter 1 : 1

Enter the element in the list : 4

If you wish to add more data on the list enter 1 : 1

Enter the element in the list : 5

If you wish to add more data on the list enter 1 : 0

Enter the data to find it's occurrence : 1
1 occured 1 times in the list
```

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