stack implementation via linked_list

stack.cpp

#include <iostream>
#include <cstring>

using namespace std;


struct node {
	int info;
	node * next;
}*start;

class ll {
	int top;
public:
	ll() {
		start = NULL;
	}
	node* create_node(int);
	void insert(int i);
	int del();
};	

class stack:public ll {
public:
	void push(int n);
	int pop();
};

int main() {
	stack s;
	s.push(30);
	s.push(32);
	s.push(23);
	cout<<s.pop()<<" "<<s.pop()<<" "<<s.pop()<<s.pop();
	return 0;
}

node* ll::create_node(int n) {
	node* temp = new node;
	if(temp==NULL) {
		cout<<"Overflow";
		return 0;
	}
	else {
		temp->info = n;
		temp->next = NULL;
		return temp;
	}
}



void ll::insert(int i) {
	node *temp, *r;
	temp = create_node(i);
	if(start==NULL) {
		start = temp;
	}
	else {
		 r = start;
        start = temp;
        start->next = r;
	}
}

int ll::del() {
	if(start==NULL) {
		cout<<"Underflow";
	}

	else {
		int s;
		s = start->info;
		node *r;
		r = start;
		start = r->next;
		return s;
	}
}

void stack::push(int n) {
	insert(n);
}

int stack::pop() {
	int n;
	n =del();
	return n;
}