C: Doubly Linked List

Soalan :
Write  a C program  to perform the  following  operations  on  a doubly linked  list:
i.  To create  a list  by adding each node  at the  front.
ii.  To display  all the  elements  in  the reverse order.

Jawapan :

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

struct linkedlist
{
 int item;
 struct linkedlist *right,*left;
};

typedef struct linkedlist node;

void main()
{
 node *start,*end;
 int choice;
 int menu(void);
 node *create(node **lastnode);
 void display(node *first,node *last);
 void insert(node **first,node **last);
 void del(node **first,node **last);
 printf("\n DOUBLY LINKED LIST");
 printf("\n ******************");
 do
 {
  printf("\n\nMain menu");
  printf("\n\n1.Create \n2.Insert \n3.Delete \n4.Display \n5.Exit");
  choice =menu();

  switch(choice)
  {
   case 1:
   printf("\n Enter the data(-999 to stop):");
   start=create(&end);
   continue;

   case 2:
   insert(&start,&end);
   printf("\n");
   continue;

   case 3:
   del(&start,&end);
   printf("\n");
   continue;

   case 4:
   display(start,end);
   printf("\n");
   continue;

   case 5:
   exit(0);

   default:
   printf("\n\nINVALID CHOICE...");
  }
 }while(1);
}

int menu()
{
 int choice;
 do
 {
  printf("\n Enter your choice:");
  scanf("%d",&choice);
  if(choice<1||choice>5)
  printf("\n Wrong choice");
 }
  while(choice<1||choice>5);
  printf("\n");
  return(choice);
}

node *create(node **lastnode)
{
 node *temp,*firstnode;
 int info;
 *lastnode=NULL;
 firstnode=NULL;
 scanf("%d",&info);

 while(info!=-999)
 {
  temp=(node *)malloc(sizeof(node));
  temp->item=info;
  temp->right=NULL;
  if(firstnode==NULL)
  {
   temp->left=NULL;
   firstnode=temp;
  }
 else
 {
  temp->left=(*lastnode);
  (*lastnode)->right=temp;
 }
 (*lastnode)=temp;
 scanf("%d",&info);
 }
if(firstnode!=NULL)
(*lastnode)=temp;
return(firstnode);
}

void display(node *first,node *last)
{
 printf("\n Forward traversal\n");
 while(first!=NULL)
 {
  printf("%d\t",first->item);
  first=first->right;
 }
  printf("\n Backward traversal\n");
  while(last!=NULL)
  {
   printf("%d\t",last->item);
   last=last->left;
  }
  return;
}

void insert(node **first,node **last)
{
 node *newnode;
 int newitem;
 int position;
 node *temp;
 int i;
 printf("\n New data item:");
 scanf("%d",&newitem);
 do
 {
  printf("\n Position of insertion:");
  scanf("%d",&position);
 }
 while(position<=0);
 if(((*first)==NULL)||(position==1))
 {
  newnode=(node *)malloc(sizeof(node));
  newnode->item=newitem;
  newnode->right=*first;
  newnode->left=NULL;
  if((*first)!=NULL)
  (*first)->left=newnode;
 else
 (*last)=newnode;
 *first=newnode;
 }
 else
 {
  i=1;
  temp=*first;
  while((i<position-1)&&(temp->right!=NULL))
  {
   i++;
   temp=temp->right;
  }
  newnode=(node *)malloc(sizeof(node));
  newnode->item=newitem;
  newnode->right=temp->right;
  if(temp->right!=NULL)
  temp->right->left=newnode;
  newnode->left=temp;
  temp->right=newnode;
 }
 if(newnode->right==NULL)
 *last=newnode;
}

void del(node **first,node **last)
{
 node *temp,*prev;
 int target;
 printf("\n Enter the data to be deleted:");
 scanf("%d",&target);

 if(*first==NULL)
  printf("\n List is empty");
 else if((*first)->item==target)
 {
  if((*first)->right==NULL)
  *first=*last=NULL;

  else
  {
   *first=(*first)->right;
   (*first)->left=NULL;
  }
 }
 else
 {
  temp=*first;
  prev=NULL;
  while((temp->right!=NULL)&&(temp->item!=target))
  {
   prev=temp;
   temp=temp->right;
  }
  if(temp->item!=target)
  printf("\n Element not found");
  else
  {
   if(temp==*last)
   *last=prev;
   else
   temp->right->left=temp->left;
   prev->right=temp->right;
  }
 }
}