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

Here, we are going to learn how to count the number of occurrences of an element in a linked list using recursion?
Submitted by Piyas Mukherjee, on January 11, 2019

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 //linked list structure
{
int data;
struct list *next;
}node;

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

int main()
{
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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