Circular Doubly Linked List: Delete at End

Circular Doubly Linked List: Delete at End

#include<stdio.h>

#include<stdlib.h>

struct node

{

                int data;

                struct node *llink;

                struct node *rlink;

};

typedef struct node* NODE;

NODE getnode();

NODE insert_at_end(NODE last, int item);

NODE delete_at_end(NODE last);

void display(NODE last);

NODE getnode()

{

                NODE x;

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

                return x;

}

NODE insert_at_end(NODE last, int item)

{

                int val;

                NODE cur, temp;

                temp = getnode();

                temp->data = item;

                if(last == NULL)

                {

                                last = temp;

                }

                else

                {

                                temp->rlink = last->rlink;

                                last->rlink->llink = temp;

                }

                last->rlink = temp;

                temp->llink = last;

                return temp;

}

NODE delete_at_end(NODE last)

{

                NODE prev, cur;

                if(last == NULL)

                {

                                printf("\nList is empty");

                                return NULL;

                }

                if(last->rlink == last)

                {

                                printf("\nThe node %d is deleted",last->data);

                                free(last);

                                return NULL;

                }

                prev = last->rlink;

                while(prev->rlink!=last)

                {

                                prev = prev->rlink;

                }

                prev->rlink=last->rlink;

                last->rlink->llink = prev;

                printf("The node %d is deleted \n",last->data);

                free(last);

                return prev;

}

void display(NODE last)

{

                NODE cur;

                printf("\nContents are:\n");

                if(last == NULL)

                                printf("\nList is empty. Nothing to display.");

                else

                {

                                 cur = last->rlink;

                                while(cur != last)

                                {

                                                printf("|%d | %d | %d | ==>  ", cur->llink, cur->data, cur->rlink);

                                                cur = cur->rlink;

                                }

                                printf("| %d | %d | %d |  ", cur->llink, cur->data, cur->rlink);

                }

}

void main()

{

                int ch, item;

                NODE last = NULL;

                while(1)

                {

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

                                printf("\n1.Insert at end");

                                printf("\n2.Delete from end");

                                printf("\n3.Display");

                                printf("\n4.exit");

                                printf("\nEnter your choice: ");

                                scanf("%d",&ch);

                                switch(ch)

                                {

                                              case 1:  printf("\nEnter the value: ");

                                                           scanf("%d", &item);

                                                           last = insert_at_end(last, item);

                                                           break;

                                                case 2:   last = delete_at_end(last);

                                                               break;

                                                case 3:   display(last);

                                                              break;

                                                case 4:   exit(0);

                                }

                }

}

Output:

~~MENU~~

1.Insert at end

2.Delete from end

3.Display

4.exit

Enter your choice: 1

Enter the value: 11

~~MENU~~

1.Insert at end

2.Delete from end

3.Display

4.exit

Enter your choice: 1

Enter the value: 12

~~MENU~~

1.Insert at end

2.Delete from end

3.Display

4.exit

Enter your choice: 1

Enter the value: 13

~~MENU~~

1.Insert at end

2.Delete from end

3.Display

4.exit

Enter your choice: 3

Contents are:

|5321840 | 11 | 5321816 | ==>  |5321792 | 12 | 5321840 | ==>  | 5321816 | 13 | 5321792 |

~~MENU~~

1.Insert at end

2.Delete from end

3.Display

4.exit

Enter your choice: 2

The node 13 is deleted

~~MENU~~

1.Insert at end

2.Delete from end

3.Display

4.exit

Enter your choice: 4