Question

So I am trying to program in C++ a linked list but I’m not sure how to do it exactly. I understand the concept more or less and I saw a tutorial that gave me this code but it didn’t explain it too well. I was wondering if you all could help me with the next steps, explain to me what I just did, and explain to me how to continue. I want it to add elements, pop or push elements in a stacked manner, last in first out, and free elements at the end and free up the memory to prevent memory leaks. thank you.

    #include <iostream>
using namespace std;

struct node
{
    int num;
    node *link;
}*p;

void main()
{
    node *root;

    root = new node;
    root->num=5;
    root->link = p;
    p = root;

    node *q;

    for(q = p; q != NULL; q = q->link)
    {
        cout<<q->num;
        cout<<endl;
    }
}

Answer 1

First of all, since you already use the standard library (#include <iostream>), be informed that the standard library already have lists: (#include <list>) as well as other containers.

You can find their documentation here

In case you want to write yourself, use a proper approach: don’t put everything into main, but define a proper class and methods to manipulate the elements. You can refer to the standard documentation I linked as a “inspiration”.

You will probably end-up with something like

class list
{
    struct element
    {
        element* pnext;
        int value;
    };

    element* root;

public:

    list() :root() 
    {}

    ~list() 
    { while(root) pop(); }

    list(const list&) =delete;

    list& operator=(const list&) =delete;

    void push(int val) 
    { 
        element* p = new element;
        p->value = val;
        p->pnext = root;
        root = p;
    }

    void pop()
    {
        element* pe = root;
        root = pe->pnext;
        delete pe;
    }

    class index
    {
        element* p;
        index(element* s) :p(s) {}
        friend class list;
    };

    index start() const const 
    { return index(root); }

    index next(index i) const 
    { return index(i.p->pnext); }

    int at(index i) const 
    { return i.p->value; }

    bool is_end(index i) const 
    { return i.p == nullptr; }
};