#include <iostream>
#include <vector>
using namespace std;

/**
 * interface of a stack
 */
class IntegerStackInterface {
public:
	// add value on top
	virtual void push(int value)  = 0;
	// remove value on top
	virtual void pop() = 0;
	// return value on top
	virtual int top() = 0;
	// tells whether stack is empty
	virtual bool is_empty() = 0;
};

/**
 * Implementation as a C array
 */
class IntegerStackAsArray : public IntegerStackInterface {
protected:
	int max_elements;
	int index;
	int *elements;
public:
	IntegerStackAsArray(int sz=10) {
		index = -1;
		elements = new int [max_elements = sz];
	}
	~IntegerStackAsArray() {
		delete [] elements;
	}
	void push(int value) {
		elements[++index] = value;
	}
	void pop() {
		--index;
	}
	int top() {
		return elements[index];
	}
	bool is_empty() {
		return (index == -1) ? true : false;
	}
};

/**
 * Implementation as a STL vector
 */
class IntegerStackAsVector : public IntegerStackInterface {
protected:
	int max_elements;
	vector<int> v;
public:
	IntegerStackAsVector(int sz=10) {
		max_elements = sz;
	}
	~IntegerStackAsVector() {
	
	}
	void push(int value) {
		v.push_back(value);
	}
	void pop() {
		v.pop_back();
	}
	int top() {
		return v[v.size()-1];
	}
	bool is_empty() {
		return (v.size() == 0) ? true : false;
	}
	
};

/**
 * treatment using pointer access
 * add values 1, 2, ..., 10
 * then compute sum by poping them
 */
void process_ptr(IntegerStackInterface *s) {
	for (int i=1; i<=10; ++i) {
		s->push(i);
	}
	int sum = 0;
	while (!s->is_empty()) {
		sum += s->top();
		s->pop();
	}
	cout << "sum = " << sum << endl;
}

/**
 * treatment using reference access
 * add values 1, 2, ..., 10
 * then compute sum by poping them
 */
void process_ref(IntegerStackInterface& s) {
	for (int i=1; i<=10; ++i) {
		s.push(i);
	}
	int sum = 0;
	while (!s.is_empty()) {
		sum += s.top();
		s.pop();
	}
	cout << "sum = " << sum << endl;
}


int main() {
	IntegerStackAsArray s1;
	IntegerStackAsVector s2;
	
	
	process_ptr(&s1);
	process_ptr(&s2);
	
	process_ref(s1);
	process_ref(s2);
}