C Program To Implement Circular Singly Linked List

If the tail node in a list gives access to the head node in the same list, then that list is called circular linked list.

                   head                         tail
                ----------------           ----------------
     +----> |data |       --|------>| data |      --|----+
     |         ----------------           ----------------     |
     |                                                                |
     +-----------------------------------------------------+


See Also:

C Program To Merge Two Arrays
C Program For Array Representation Of Sparse Matrix
C Program To Perform Insertion, Deletion, Searching & Traversal In Singly Linked List
C Program To Perform Insertion, Deletion, Sorting In Doubly Linked List - (Simple)
C Program To Sort A Doubly Linked List (Descending Order)

C Program To Merge Two Linked Lists

C Program To Reverse Linked List
C Program To Implement Circular Singly Linked List
C Program To Implement Circular Doubly Linked List
C Program For Polynomial Multiplication Using Linked List 
C Program For Polynomial Addition Using Linked List
C Program For Linked List Representation Of Sparse Matrix
C Program To Concatenate Two Linked Lists
C Program To Perform Recursion On Linked List

Insertion, Deletion, Traversal, Reversal And Search Operation on Arrays
Doubly Linked List - Insertion, Traversal, Searching, Delete Node, Delete List

Example Program For Circular Singly Linked List Implementation(in C):

---

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

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

  struct node *head = NULL, *tail = NULL;

  struct node * createNode(int data) {
        struct node *newnode;
        newnode = (struct node *)malloc(sizeof (struct node));
        newnode->data = data;
        newnode->next = NULL;
  }

    /*
     * create dummy head and tail to make
     * insertion and deletion operation simple.
     * While processing data in our circular 
     * linked list, skip these dummies.
     */

  void createDummies() {
        head = createNode(0);
        tail = createNode(0);
        head->next = tail;
        tail->next = head;
  }

  /* insert data next to dummy head */

  void circularListInsertion(int data) {

        struct node *newnode, *temp;

        newnode = createNode(data);

        temp = head->next;

        head->next = newnode;

        newnode->next = temp;

  }

  /* Delete the node that has the given data */

  void DeleteInCircularList(int data) {

        struct node *temp0, *temp;

        if (head->next == tail && tail->next == head) {

                printf("Circular Queue/list is empty\n");

        }

        temp0 = head;

        temp = head->next;

        while (temp != tail) {

                if (temp->data == data) {

                        temp0->next = temp->next;

                        free(temp);

                        break;

                }

                temp0 = temp;

                temp = temp->next;

        }

        return;

  }

  /*

   * travese the circular linked list for

   * the given no of times.

   */

  void display(int count) {

        int n = 0;

        struct node *tmp = head;

        if (head->next == tail && tail->next == head) {

                printf("Circular linked list is empty\n");

                return;

        }

        while (1) {

                /* skip the data in dummy head and tail */

                if (tmp == head || tmp == tail) {

                        if (tmp == tail) {

                                n++;

                                printf("\n");

                                if (n == count)

                                        break;

                        } else {

                                tmp = tmp->next;

                                continue;

                        }

                } else {

                        printf("%-3d", tmp->data);

                }

                tmp = tmp->next;

        }

        return;

  }

  int main() {

        int data, ch, count;

        createDummies();

        while (1) {

                printf("1. Insertion\t2. Deletion\n");

                printf("3. Display\t4. Exit\n");

                printf("Enter ur choice:");

                scanf("%d", &ch);

                switch (ch) {

                        case 1:

                                printf("Enter the data to insert:");

                                scanf("%d", &data);

                                circularListInsertion(data);

                                break;

                        case 2:

                                printf("Enter the data to delete:");

                                scanf("%d", &data);

                                DeleteInCircularList(data);

                                break;

                        case 3:

                                printf("No of time u wanna traverse:");

                                scanf("%d", &count);

                                display(count);

                                break;

                        case 4:

                                exit(0);

                        default:

                                printf("Pls. enter correct option\n");

                                break;

                }

        }

        return 0;

  }

  Output: (Insertion, Deletion, Traversal In Circular Singly Linked List)

  jp@jp-VirtualBox:~/cpgms/data_structures$ ./a.out
  1. Insertion 2. Deletion
  3. Display 4. Exit
  Enter ur choice:1
  Enter the data to insert:10
  1. Insertion 2. Deletion
  3. Display 4. Exit
  Enter ur choice:1
  Enter the data to insert:20
  1. Insertion 2. Deletion
  3. Display 4. Exit
  Enter ur choice:1
  Enter the data to insert:30
  1. Insertion 2. Deletion
  3. Display 4. Exit
  Enter ur choice:3
  No of time u wanna traverse:3
  30 20 10 
  30 20 10 
  30 20 10 
  1. Insertion 2. Deletion
  3. Display 4. Exit
  Enter ur choice:2
  Enter the data to delete:20
  1. Insertion 2. Deletion
  3. Display 4. Exit
  Enter ur choice:3
  No of time u wanna traverse:2
  30 10 
  30 10 
  1. Insertion 2. Deletion
  3. Display 4. Exit
  Enter ur choice:4