C Programming language

Since by using doubly linked list the deletion of the nodes or elements have become quite very easy in a list. Just by doing few minor pointer changes we can perform various deletion operations. Following is the program which shows how we can delete a node from the list.

#include<stdio.h>
#include<conio.h>
#include<malloc.h>
#include<process.h>
struct node
    {
int num;
struct node *next;
struct node *prev;
};                             /* declaring a global node of type struct */
typedef struct node NODE;     /* providing a type definition to the above created structure */
NODE *head=NULL;             /* declaring some of the global variable that would be used throughout the program */
NODE *temp, *first, *last;
int info;
void display();
void create_list();
void del_at_begin();
void del_at_end();
void del_at_specifiedpos();
void main()                                           /* starting the main method() */
{
int i;
clrscr();
printf("\nprogram for deletion in a doubly linked list :\n");
do
{
printf("\nEnter your choice :\n");          /*    creating menu for various insertion operations on the list */
printf("\n1.Create a linked list :");
printf("\n2.Delete from the front in the linked list :");
printf("\n3.Delete from the end position in the linked list :");
printf("\n4.Delete at any specified position in the linked list :");
printf("\n5.Exit\n");
fflush(stdin);
scanf("\n%d",&i);
switch(i)
{
case 1:
create_list();
display();
case 2:
del_at_begin();
display();
break;
case 3:
del_at_end();
display();
break;
case 4:
del_at_specifiedpos();
display();
break;
case 5:
exit(0);
}
}
while(i<=5);
getch();
}
void create_list()
{
printf("\nEnter your element in the linked list :");         /*creating a doubly linked list */
scanf("%d",&info);
temp=(NODE *)malloc(sizeof(NODE)); /* allocating memory for the node to be inserted */
temp->num=info;
temp->next=NULL;
temp->prev=NULL;
if(head==NULL)                       /* checking whether list is empty */
{
head=temp;
first=temp;
last=temp;
}
else                             /*inserting at the end of the list*/
{
first=head;
while(first->next!=last)
{
first=first->next;
}
first->next=temp;
temp->prev=first;
temp->next=NULL;
last=temp;
}
}
void display()
{
if(head==NULL)
printf("linked list is empty");
else
{
    first=head;
    printf("\nStatus of the linked list is as follows :\n");
     while(first->next!=last)           /* traversing the linked list */
     {
      printf("\n%d",first->num);
      first=first->next;
     }
    }
}
void del_at_begin()
{
if(head==NULL)
{
     printf("linked list is empty");
}
else
{
    temp=head;
head=head->next;
head->prev=NULL;
free(temp);
}

}
void del_at_end()
{
if(head==NULL)

{
printf("\nlinked list is empty");
}
else
{
     temp=head;
while(temp->next!=last)
{
temp=temp->next;
}
    last=temp->prev;
last->next=NULL
free(temp);
}
}
void del_at_specifiedpos()
{
int node_num;
if(head==NULL)
{
    printf("\nlinked list is empty");
}
else
{
    temp=head;
printf("\nEnter the position of the node you want to delete");
scanf("\n%d",&node_num);
    for(int i=1;i<node_num;i++)
{
     second=temp;
temp=temp->next;
}
first=temp->next;
second->next=temp->next;
first->prev=temp->prev;
free(temp);
}
}

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