# C - Circular Singly Linked List

A circular singly linked list is a linear data structure, in which the elements are stored in the form of a node. Each node contains two sub-elements. A data part that stores the value of the element and the next part that stores the pointer to the next node as shown in the below image:

The first node also known as HEAD is always used as a reference to traverse the list. The last node points to HEAD. A circular singly linked list can be visualized as a chain of nodes, where every node points to the next node. Along with this, next of the last node is linked to the head node.

## Implementation of Circular Singly Linked List

### Representation:

In C, a node can be created using structure as shown below:

//node structure struct Node { int data; struct Node* next; };

### Create a Circular Singly Linked List

Let us create a simple circular singly linked list which contains three data nodes.

#include <stdio.h> #include <stdlib.h> //node structure struct Node { int data; struct Node* next; }; // test the code int main() { //create the head node with name MyList struct Node* MyList = NULL; //Add first node. struct Node* first; //allocate second node in the heap first = (struct Node*)malloc(sizeof(struct Node)); first->data = 10; //linking with head node MyList = first; //linking next of the node with head first->next = MyList; //Add second node. struct Node* second; //allocate second node in the heap second = (struct Node*)malloc(sizeof(struct Node)); second->data = 20; //linking with first node first->next = second; //linking next of the node with head second->next = MyList; //Add third node. struct Node* third; //allocate third node in the heap third = (struct Node*)malloc(sizeof(struct Node)); third->data = 30; //linking with second node second->next = third; //linking next of the node with head third->next = MyList; return 0; }

### Traverse a Circular Singly Linked List

A circular singly linked list can be traversed from any node of the list using a temp node. Keep on moving the temp node to the next one and displaying its content. Stop the traversal, after reaching the starting node.

#include <stdio.h> #include <stdlib.h> //node structure struct Node { int data; struct Node* next; }; //display the content of the list void PrintList(struct Node* head_ref) { struct Node* temp = head_ref; if(head_ref != NULL) { printf("\nThe list contains: "); while (1) { printf("%i ",temp->data); temp = temp->next; if(temp == head_ref) break; } } else { printf("\nThe list is empty."); } } // test the code int main() { //create the head node with name MyList struct Node* MyList = NULL; //Add first node. struct Node* first; //allocate second node in the heap first = (struct Node*)malloc(sizeof(struct Node)); first->data = 10; //linking with head node MyList = first; //linking next of the node with head first->next = MyList; //Add second node. struct Node* second; //allocate second node in the heap second = (struct Node*)malloc(sizeof(struct Node)); second->data = 20; //linking with first node first->next = second; //linking next of the node with head second->next = MyList; //Add third node. struct Node* third; //allocate third node in the heap third = (struct Node*)malloc(sizeof(struct Node)); third->data = 30; //linking with second node second->next = third; //linking next of the node with head third->next = MyList; //print the content of list PrintList(MyList); return 0; }

The above code will give the following output:

The list contains: 10 20 30