Singly Linked List using Arrays: It's crashing on run-time

Question

Whats wrong with this code? I am writing this code to implement singly linked list using arrays but its not working. Im using code::blocks and its crashing on run time. Please help. I must have missed out on something when it was taught in the class. xD

#include<iostream>
#include<stdio.h>
using namespace std;
class Node
{
 int data;
 Node *next;
public:
 Node(int n)
 {
 data=n;
 next=NULL;
 }
 friend class List;
};
class List
{
 Node *listptr;
public:
void create();
void display();
};
void List::create()
{
 Node *temp;
 int n, num;
 cout << "Enter number of nodes:" << endl;
 cin >> n;
 cout << "/nEnter the data" << endl;
 for(int i=0; i<n; i++)
 {
 cin >> num;
 Node *new_node=new Node(num);
 if(listptr==NULL)
 listptr=temp=new_node;
 else
 {
 temp->next=new_node;
 temp=temp->next;
 }
 }
}
void List::display()
{
 Node *temp=listptr;
 while(temp!=NULL)
 {
 cout << temp->data << "->";
 temp=temp->next;
 }
}
 main()
{
 List l1;
 l1.create();
 l1.display();
}

• Some programmer dude: I recommend you learn how to debug your programs. Especially how to use a debugger to catch crashes and location where they happen.
• nwp: Looking at the code I'm confused if this is supposed to be C or C++ too.
• AndyG: Node *temp; is never initialized.
• Rajan Pandey: @Someprogrammerdude okay I'll learn it! thanks a ton! :)
• molbdnilo: You haven't used any array. If you're supposed to do that, you probably should.

Answer 1

listptr not initialized, you can initialize in constructor.

 List() {
 listptr = 0;
 }

Class List should be

class List
{
 Node *listptr;
 public:
 List() {
 listptr = 0;
 }
 void create();
 void display();
};

• Rajan Pandey: OMG you are a life saver! Thanks a lot!

Answer 2

Try following piece of code -

First Creating Node

class ListElement
{
 int data;
 ListElement* next;
public:
 void set_element(int item) { data = item; }
 int get_value() { return data; }
 friend class List;
};

Another class for further operation

class List
{
 ListElement *Start, *Tail, *New;
public:
 List() { Start = Tail = New = NULL; } // initialise all pointer value to NULL
 void add_element(int element) {
 // Create a new Node
 New = new ListElement;
 New->set_element(element);
 New->next = NULL;
 // adding value or linkig each node to each other
 (Start == NULL) ? Start = New : Tail->next = New;
 Tail = New;
 }
 // print the whole linked list
 void print()
 {
 ListElement* Current = Start;
 while (Current != NULL)
 {
 cout << Current->get_value() << endl;
 Current = Current->next;
 }
 }
};

Main Function

int main()
{
 List L;
 int num_of_element, element;
 cin >> num_of_element;
 for (int i(0); i < num_of_element; i++) {
 cin >> element;
 L.add_element(element);
 }
 L.print();
}

Hope it'll work.