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();
}

I recommend you learn how to debug your programs. Especially how to use a debugger to catch crashes and location where they happen. — Some programmer dude
– Some programmer dude, Commented Jan 15, 2018 at 15:04
Looking at the code I'm confused if this is supposed to be C or C++ too. — nwp
– nwp, Commented Jan 15, 2018 at 15:04
You haven't used any array. If you're supposed to do that, you probably should. — molbdnilo
– molbdnilo, Commented Jan 15, 2018 at 15:17

Achal · Accepted Answer · 2018-01-15 15:07:58Z

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();
};

edited Jan 15, 2018 at 15:07

answered Jan 15, 2018 at 15:06

Achal

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1 Comment

Rajan Pandey Over a year ago

OMG you are a life saver! Thanks a lot!

Innat · Accepted Answer · 2018-05-19 12:31:19Z

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.

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