Doubly Linked List: Delete from End

Doubly Linked List: Delete from End

#include<stdio.h>

#include<string.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 first, int item);

NODE delete_at_end(NODE first);

void display(NODE first);

NODE getnode()

{

            NODE x;

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

            x->llink=NULL;

            x->rlink=NULL;

            return x;

}

void display(NODE first)

{

            NODE cur;

            cur = first;

            printf("\nContents are:");

            if(cur == NULL)

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

            else

            {

                        while(cur!=NULL)

                        {

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

                                    cur = cur->rlink;

                        }

            }

}

NODE insert_at_end(NODE first, int item)

{

            int val;

            NODE cur, temp;

            temp = getnode();

            temp->data = item;

       

            if(first == NULL)                               /*Case 1: List is empty*/

            {

                        return temp;

            }         

            cur= first;                                            /*Case 2: List not empty*/

            while(cur->rlink!=NULL)

            {

                        cur = cur->rlink;

            }

            cur->rlink = temp;

            temp->llink = cur;

            return first;

}

NODE delete_at_end(NODE first)

{

            NODE prev=NULL, cur;

            if(first == NULL)                                           /*Case 1: List is empty*/

            {

                        printf("\nList is empty. Cannot delete.");

                        return NULL;

            }

            if(first->rlink == NULL)                              /*Case 2: List has only one node*/

            {

                        printf("\nItem that got deleted is %d", first->data);

                        free(first);

                        return NULL;

            }         

            cur = first;                                           /*Case 3: List is not empty*/

            while(cur->rlink!=NULL)

            {

                        prev = cur;

                        cur = cur->rlink;

            }

            prev->rlink = NULL;              /*Delete the Last node. Update the prev node’s pointer*/

            printf("\nItem that got deleted is %d", cur->data);

            free(cur);

            return first;

}

void main()

{

            int ch, item;

            NODE first = 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)     ;

                                                            first = insert_at_end(first, item);

                                                            break;

                                    case 2:             first = delete_at_end(first);

                                                            break;

                                    case 3:             display(first);

                                                            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: 3

Contents are: 11        12

~~MENU~~

1.Insert at end

2.Delete from end

3.Display

4.exit

Enter your choice: 2

Item that got deleted is 12

~~MENU~~

1.Insert at end

2.Delete from end

3.Display

4.exit

Enter your choice: 2

Item that got deleted is 11

 ~~MENU~~

1.Insert at end

2.Delete from end

3.Display

4.exit

Enter your choice: 2

List is empty. Cannot delete.

~~MENU~~

1.Insert at end

2.Delete from end

3.Display

4.exit

Enter your choice: 3

Contents are:

List is empty. Nothing to display.