How to print linked list using c++ recursion in object oriented form (OOP)

Question

i m just creating my on stack using linked list,but when i print elements using recursion it exit with random code in geany.

#include <iostream>
using namespace std;
class Node
{
    public:
    int data;
    Node* next;
};
class Stack
{
    public:
    Node* Top;
    void stack()
    {
        Top = NULL;
    }
    void pop()
    {
        if(Top == NULL)
        {
            cout<<"\nstack empty";
        }
        Top = Top->next;
    }
    
    void push(int data)
    {
        Node* newNode = new Node();
        newNode->data = data;
        newNode->next = Top;
        Top = newNode;
    }
    
    bool isEmpty()
    {
        if(Top == NULL)
        {
            return true;
        }
        else
        {
            return false;
        }
    }
    void print()
    {
        tem_print(Top);
    }
    
    void tem_print(Node* t_top)
    {
        if(t_top == NULL)
        {
            return;
        }
        tem_print(t_top->next);
        cout<<t_top->data;
    }
};
int main()
{
    Stack s;
    s.push(1);
    s.push(2);
    s.print();
    return 0;
}

i used a print() function inside it i called another temp print function which is used to print elements,It works fine if i used iteration method to print

output: freeze of 3sec

and prints this

(program exited with code: -1073741819)

Press any key to continue . . .

No part of your code ever initializes a Node with next set to NULL, so your condition can never be true — UnholySheep
– UnholySheep, Commented Aug 8, 2020 at 15:33
I'm also fairly certain that you meant void stack() to be the constructor Stack() instead — UnholySheep
– UnholySheep, Commented Aug 8, 2020 at 15:34
in push funtion i initialized newNode->next = Top, where Top is null so when adding new node we automatically set last node to null — Aarav
– Aarav, Commented Aug 8, 2020 at 15:34
Top is never NULL in your code because you never set it to be so — UnholySheep
– UnholySheep, Commented Aug 8, 2020 at 15:36

cigien · Accepted Answer · 2020-08-08 15:41:03Z

3

You are not initializing Top in your code, so the first time you read from it, you are invoking undefined behavior (UB). The result of a program with UB could be anything, including freezing for some time, or exiting with an error code.

This function:

void stack()
    {
        Top = NULL;
    }

looks suspiciously like a constructor. If so, you need to write:

Stack()
    {
        Top = NULL;
    }

or even better:

Stack() : Top(NULL) {}

In fact, you don't even need a constructor if you just initialize Top when you declare it inside the class.

Also, in your pop function, you are accessing next even if Top is NULL. Instead, you need an else statement:

void pop()
    {
        if(Top == NULL)
        {
            cout<<"\nstack empty";
        }
        else   // needed to avoid UB
            Top = Top->next;
    }

Here's a demo.

Also, you should avoid using NULL in your code: use nullptr instead. Finally, please avoid using using namespace std;, it's a bad habit.

edited Aug 8, 2020 at 15:41

answered Aug 8, 2020 at 15:36

cigien

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2 Comments

Aarav Over a year ago

why did you deleted all the comments.. :D

cigien Over a year ago

I didn't delete them, as far as I recall :) I don't remember what the comments were about, but they get deleted if they are not relevant to the post.

CiaPan · Accepted Answer · 2020-08-08 15:43:51Z

1

Your pop function performs Top = Top->next; even if Top == NULL.

answered Aug 8, 2020 at 15:43

CiaPan

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2 Comments

Aarav Over a year ago

will be adding return statement. so it won't execute that line.

Aarav Over a year ago

and thanks for helping and using your time to check it. :D

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