Friday, 23 September 2016

Circular Singly Linked List: Delete from Front

Circular Singly Linked List: Delete from Front


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

struct node
{
                int data;
                struct node *link;
};
typedef struct node* NODE;

NODE getnode();
NODE insert_at_front(NODE last,int item);
NODE delete_at_front(NODE last);
NODE display(NODE last);

NODE getnode()
{
                NODE x;
                x =(NODE) malloc(sizeof(struct node));
                return x;
}

NODE insert_at_front(NODE last, int item)
{
                NODE temp;
                temp = getnode();
                temp->data = item;
                if(last == NULL)                                                    /*Case 1: List is empty*/
                {
                                last = temp;
                }
                else                                                                        /*Case 2: If not empty*/
                {
                                temp->link = last->link;
                }
                last->link = temp;
                return last;
}

NODE delete_at_front(NODE last)
{
                NODE temp;
                if(last == NULL)
                {
                                printf("\n List is empty");
                                return NULL;
                }
                if(last->link == last)
                {
                                printf("\nThe node %d is deleted", last->data);
                                free(last);
                                return NULL;
                }
                temp = last->link;
                last->link = temp->link;
                printf("\nThe node  %d is deleted", temp->data);
                free(temp);
                return last;
}

void display(NODE last)
{
                NODE cur;
                printf("\nContents are:\n");
                if(last == NULL)
                                printf("\nList is empty. Nothing to display.");
                else
                {
                                cur = last->link;
                                printf("==> ");
                                while(cur != last)
                                {
                                                printf("| %d | %d | => ", cur->data, cur->link);
                                                cur = cur->link;
                                }
                                printf("| %d | %d | => ", cur->data, cur->link);
                 }
}

void main()
{
                int ch, item;
                NODE last = NULL;
                while(1)
                {
                                printf("\n\n~~MENU~~");
                                printf("\n1.Insert at front");
                                printf("\n2.Delete from front");
                                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_front(last, item);
                                                               break;
                                                case 2:    last = delete_at_front(last);
                                                               break;
                                                case 3:    display(last);
                                                               break;
                                                case 4:    exit(0);
                                }
    }
}

Output:
~~MENU~~
1.Insert at front
2.Delete from front
3.Display
4.exit
Enter your choice: 1
Enter the value: 11

~~MENU~~
1.Insert at front
2.Delete from front
3.Display
4.exit
Enter your choice: 3
Contents are:
==> | 11 | 7214960 | =>

~~MENU~~
1.Insert at front
2.Delete from front
3.Display
4.exit
Enter your choice: 1
Enter the value: 12

~~MENU~~
1.Insert at front
2.Delete from front
3.Display
4.exit
Enter your choice: 3
Contents are:
==> | 12 | 7214960 | => | 11 | 7214856 | =>

~~MENU~~
1.Insert at front
2.Delete from front
3.Display
4.exit
Enter your choice: 2
The node  12 is deleted
~~MENU~~
1.Insert at front
2.Delete from front
3.Display
4.exit
Enter your choice: 2
The node 11 is deleted

~~MENU~~
1.Insert at front
2.Delete from front
3.Display
4.exit
Enter your choice: 2
List is empty

~~MENU~~
1.Insert at front
2.Delete from front
3.Display
4.exit
Enter your choice: 3
Contents are:
List is empty. Nothing to display.

~~MENU~~
1.Insert at front
2.Delete from front
3.Display
4.exit
Enter your choice: 4



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