# Convert a given singly linked list to a circular list | C program

Here, we are going to learn how to convert a given singly linked list to a circular list using C program?
Submitted by Piyas Mukherjee, on January 30, 2019

Algorithm:

Function: slltocll()

Input: A singly linked list whose address of the first node is stored in a pointer, say head

Output: The same circular linked list

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
while(temp->next!=NULL)
begin
temp=temp->next
end While
End
```

C code:

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

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

void display(node *temp)
{
node *temp1=temp;
printf("The list is as follows :\n%d->",temp->data);
temp=temp->next;
//which not circle back to head node
while(temp!=temp1)
{
printf("%d->",temp->data);
temp=temp->next;
}
printf("%d\n",temp1->data);

return;
}

int main(){
int choice,count=0,key;

//Taking the linked list as input
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 m ore data on the list enter 1 : ");
scanf("%d",&choice);
}while(choice==1);

//In order to convert a singly linked list to a
//circular singly linked list we just need to copy
//the address of the head node to the next of the last node
//travarsing to the last node
while(temp->next!=NULL)
{
temp=temp->next;
}
//of the last node.....now it is a circular singly linked list

return 0;
}
```

Output

```Enter the element in the list : 1

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

Enter the element in the list : 2

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

Enter the element in the list : 3

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

Enter the element in the list : 4

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

Enter the element in the list : 5

If you wish to add m ore data on the list enter 1 : 0
The list is as follows :
1->2->3->4->5->1
```

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