Thread: Double linked list

Can someone help me turn this little program I wrote (with the assistance of someone else on this board, thanks) into a program that creates a doubly linked list instead of singly? Thanks

#include <iostream.h>
#include <stddef.h>
#include <fstream.h>

struct Node
{
int ID;
Node *Next;
};

void createlistKB(Node * &First);
void createlistFL(Node * &First);
void deletelistelement(Node* &First);
void printlist(Node * &First);
void InsertNode(Node* &First, Node* &toInsert);
int DeleteNode(Node* &First, Node* &toDelete);
int menu();




void InsertNode(Node* &First, Node* &toInsert)
{
Node* Iterator = First;


while(toInsert->ID>Iterator->ID&& Iterator->Next!=NULL)
Iterator=Iterator->Next;

if(toInsert->ID>Iterator->ID)
{
Node* Temp = Iterator->Next;
Iterator->Next=toInsert;
toInsert->Next=Temp;
}
else
{
if(Iterator==First)
{
Node* Temp = First;
First=toInsert;
toInsert->Next=Temp;
return;
}

Node* Prev = First;

while(Prev->Next!=Iterator)
Prev=Prev->Next;

Prev->Next=toInsert;
toInsert->Next=Iterator;
}


}

int DeleteNode(Node* &First, Node* &toDelete)
{
Node* Iterator = First;
Node* DelayedIterator = Iterator;
int found=0;

if(Iterator->ID==toDelete->ID)
First=First->Next;
while(Iterator!=NULL)
{
if(Iterator->ID==toDelete->ID)
{

found=1;
DelayedIterator->Next=Iterator->Next;
}

DelayedIterator=Iterator;
Iterator=Iterator->Next;
}
return found;
}

void deletelistelement(Node* &First)
{
Node* toDelete;
toDelete = new Node;
int IDtoDelete, found=0;
toDelete->Next=NULL;
cout << "Enter ID to be deleted (-999 to cancel): ";
cin >> IDtoDelete;
if(IDtoDelete==-999)
{
cout << endl;
return;
}
toDelete->ID=IDtoDelete;
found = DeleteNode(First, toDelete);
if(found==0)
cout << "ID not located\n\n";
if(found==1)
cout << "ID deleted\n\n";
}


void createlistKB(Node * &First)
{

First = new Node;
First->Next=NULL;
int potentialfirst;
cout << "Enter ID (-999 to quit): ";
cin >> potentialfirst;
if(potentialfirst==-999)
{
cout << "List was not created!";
return;
}
First->ID=potentialfirst;
Node* Temp;

for(;
{
int input=0;
cout << "Enter ID (-999 to quit): ";
cin>>input;
if(input==-999)break;

Temp = new Node;
Temp->ID=input;
Temp->Next=NULL;

InsertNode(First,Temp);
}
cout << endl;
}

void createlistFL(Node * &First)
{

First = new Node;
First->Next=NULL;
char filename[20];
cout << "File name: ";
cin >> filename;
ifstream file(filename);
if(!file.is_open())
{
cout << "ERROR: File not found!\n";
return;
}
file >> First->ID;
Node* Temp;

for(;
{
int input=0;
file>>input;
if(file.eof())break;

Temp = new Node;
Temp->ID=input;
Temp->Next=NULL;

InsertNode(First,Temp);
}
cout << "File succesfully read!\n\n";
file.close();
}

void printlist(Node * &First)
{
cout << "Here is your list!\n";
cout << "------------------\n";
Node * Temp;
Temp = First;
while(Temp!=NULL)
{
cout << Temp->ID << '\n';
Temp = Temp->Next;
}
cout << "THANK YOU!!!\n\n";
}

int menu(int modeflag)
{
int Choice;
if(modeflag==1)
cout << "Linked List Assignment\n";
if(modeflag==2)
cout << "Invalid Choice\n";
if(modeflag==3)
cout << "Make Selection\n";
cout << "-------------------------------\n";
cout << "1) Create list: Key board input\n";
cout << "2) Create list: File input\n";
cout << "3) Delete an element\n";
cout << "4) Print List\n";
cout << "5) Quit\n";
cout << "-------------------------------\n";
cin >> Choice;
cout << '\n';
return Choice;
}

void main()
{
Node *First;
First = new Node;
int modeflag=1;
First->ID=-999;
int Choice = 0;
do
{
Choice = menu(modeflag);
if(modeflag==1)
modeflag=0;
if(Choice == 1)
{
modeflag=3;
createlistKB(* &First);
}
if(Choice == 2)
{
modeflag=3;
createlistFL(* &First);
}
if(Choice == 3)
if(First->ID==-999)
{
modeflag=2;
cout << "List does not exist.\nPlease create a list first.\n\n";
}
else
{
modeflag=3;
deletelistelement(* &First);
}
if (Choice == 4)
if(First->ID==-999)
{
modeflag=2;
cout << "List does not exist.\nPlease create a list first.\n\n";
}
else
{
modeflag=3;
printlist(* &First);
}
}while(Choice!=5);
cout << "Thank you!\n";
}




sorry about the lack of indentions, I don't know how to write it on here so that it doesn't trash the indentions when I post to the board. Thanks for your help.

This compiles with zero problems in Visual C++ 6.0, and Codewarrior (aka: Satan)

Unfortunately I don't have time to redo your program for you, so i'll just give you a basic doubly linked list template.

Code:

#include <iostream.h>

class Node{
  int data;
  Node *next;
  Node *prev;
};

int main(){
  Node root = new Node;
  Node counter = new Node;
  root->data=0;
  root->next=NULL;
  root->prev=NULL;
  counter=root;
  for(int i=1; i<10; i++){  //create the list
    counter->next = new Node;
    counter->next->data=i;
    counter->next->next = NULL;
    counter->next->prev = counter;
    counter=counter->next;
  }
}