Circular Linked List with Header Node: Delete from Front

Circular Linked List with Header Node: Delete from Front

#include<stdio.h>

#include<stdlib.h>

struct node

{

            int data;

            struct node *link;

};

typedef struct node* NODE;

int count = 0;              /* To count no of nodes in the list and put it into header node */

NODE getnode()

{

            NODE x;

            x = (NODE)malloc(sizeof(struct node));

            return x;

}

NODE insert_at_front(NODE head, int item)

{

            NODE temp;

            temp = getnode();

            temp->data = item;

            temp->link = head->link;

            head->link = temp;

            head->data = ++count;

            return head;

}

NODE delete_at_front(NODE head)

{

            NODE cur;

            if(head->link == head)

            {

                        printf("\nCLL is empty.");

                        return head;

            }

            cur = head->link;

            head->link = cur->link;

            printf("\nNode with item %d is deleted", cur->data);

            free(cur);

            head->data = --count;

            return head;

}

void display(NODE head)

{

            NODE temp;

            if(head->link == head)

            {

                        printf("\nList is empty.");

                        return;

            }

            printf("\nContents of the CLL:\n");

            printf("\nNo of nodes in the CLL is %d\n", head->data);

            temp = head->link;

            while(temp!=head)

            {

                        printf("|%d|%d| --> ",temp->data, temp->link);

                        temp = temp->link;

            }

}

void main()

{

            int ch, item;

            NODE head;

            head = getnode();

            head->data = 0;

            head->link = head;                  /*Empty header node*/

            while(1)

            {

                        printf("\n~~MENU~~");

                        printf("\n1:Insert at Front \n2.Delete at Front \n3:Display \n4:Exit \n");

                        printf("Enter the choice: ");

                        scanf("%d",&ch);

                        switch(ch)

                        {

                                    case 1: printf("\nEnter the item to be inserted : ");

                                                scanf("%d", &item);

                                                head = insert_at_front(head, item);

                                                break;

                                    case 2: head = delete_at_front(head);

                                                break;

                                    case 3: display(head);

                                                break;

                                    case 4: exit(0);

                        }

            }

}

Output:

~~MENU~~

1:Insert at Front

2.Delete at Front

3:Display

4:Exit

Enter the choice: 1

Enter the item to be inserted : 11

~~MENU~~

1:Insert at Front

2.Delete at Front

3:Display

4:Exit

Enter the choice: 1

Enter the item to be inserted : 12

~~MENU~~

1:Insert at Front

2.Delete at Front

3:Display

4:Exit

Enter the choice: 1

Enter the item to be inserted : 14

~~MENU~~

1:Insert at Front

2.Delete at Front

3:Display

4:Exit

Enter the choice: 3

Contents of the CLL:

No of nodes in the CLL is 3

|14|7615608| --> |12|7608072| --> |11|7608176| -->

~~MENU~~

1:Insert at Front

2.Delete at Front

3:Display

4:Exit

Enter the choice: 2

Node with item 14 is deleted

~~MENU~~

1:Insert at Front

2.Delete at Front

3:Display

4:Exit

Enter the choice: 3

Contents of the CLL:

No of nodes in the CLL is 2

|12|7608072| --> |11|7608176| -->

~~MENU~~

1:Insert at Front

2.Delete at Front

3:Display

4:Exit

Enter the choice: 4