Range-based loop for linked list - c++14

Question

I guess I am missing something in operator ++(). I want to implement Range based loop in following Linked list code. I am not sure what I am missing in it.
struct Node {
Node() {}
Node(int e, Node* n) : elem(e), next(n) { }
int elem = 0;
Node* next = nullptr;
Node& operator ++() {
Node* current = this;
if( current != nullptr ) {
current = current->next;
return *current;
}
}
int& operator *() {
return this->elem;
}
bool operator !=(Node const& rhs) const {
return this->elem != rhs.elem;
}
int* begin() {
return &this->elem;
}
int* end() {
return nullptr;
}
};
void add(Node& n, int x) {
n.next = new Node(x, n.next);
}
int main() {
Node head;
add(head, 1);
add(head, 2);
add(head, 3);
add(head, 4);
add(head, 5);
for (int x : head) {
std::cout << x << " ";
}
std::cout << "2nd " << std::endl;
std::cout << std::endl;
for (int& x : head) {
x = 7;
}
std::cout << "3rd " << std::endl;
for (const int& x : head) {
std::cout << x << " ";
}
std::cout << std::endl;
return 0;
}
I am not sure what to add in ++ operator. I want it in same struct instead of having separate Iterator class.

Answer 1

The Node structure contains a single int element. This int element is totally unrelated to any other nodes int element.
What you do with begin and the increment operator ++ is treat one nodes int element as the first element of an array. That means your code will immediately go out of bounds.
To solve your iteration problem I first suggest that you abstract out the list and the nodes into different structures. Then you can easily make a wrapper structure which contains a pointer to the current node in the list iteration. This wrapper structure then need to overload the ++ operator which will the go to the next node in the list.
Somewhat graphically it could be something like
+------+ +--------+ +--------+ +--------+
| list | --> | node 1 | --> | node 2 | --> | node 3 | --> ...
+------+ +--------+ +--------+ +--------+
^
|
+----------+
| iterator |
+----------+
Then you increment the iterator you get this:
+------+ +--------+ +--------+ +--------+
| list | --> | node 1 | --> | node 2 | --> | node 3 | --> ...
+------+ +--------+ +--------+ +--------+
^
|
+----------+
| iterator |
+----------+
And so on...