#include<iostream>
#include<memory> 
#include<string>
using std::string;
using std::cout;
using std::endl;
using std::cin;
using std::allocator;
using std::_MAX;
using std::uninitialized_copy;
using std::uninitialized_fill;
template <class T> class Vec
{
public:
	typedef T* iterator;
	typedef const T* const_iterator;
	typedef size_t size_type;
	typedef T value_type;

	Vec() { create(); }
	explicit Vec(size_type n,const T& t=T()) { create(n,t);}
	
	Vec(const Vec& v) { create(v.begin(),v.end()); }
	Vec& operator=(const Vec&);
	~Vec() { uncreate();}

	T& operator[](size_type i) { return data[i]; }
	const T& operator[](size_type i) const {return data[i];}

	void push_back(const T& t)
	{
		if(avail==limit)
			grow();
		unchecked_append(t);
	}

	iterator erase(iterator);
	void clear();

	size_type size() const {return avail-data;}

	iterator begin() { return data;}
	const_iterator begin() const { return data;}

	iterator end() { return avail;}
	const_iterator end() const { return avail; }
private:
	iterator data;		//first element in the Vec
	iterator avail;		//(one past) the last of element in the Vec
	iterator limit;		//(one past) the allocated menory

	//facilities for memory allocation
	allocator<T> alloc;	//object to handle memory allocation
	
	//allocation and initialize the underlying array
	void create();
	void create(size_type,const T&);
	void create(const_iterator, const_iterator);

	//destroy the element in the array and free the memory
	void uncreate();

	//support funcions for push_back
	void grow();
	void unchecked_append(const T&);

};

template<class T>
Vec<T>& Vec<T>::operator =(const Vec& rhs)
{
	//check for self-assignment
	if(&rhs!=this)
	{
		//free the array in the left-hand side
		uncreate();
		//copy elements from the right-hand to the left-hand side
		create(rhs.begin(),rhs.end());
	}
	return *this;
}
template <class T> void Vec<T>::create()
{
	data=avail=limit=0;
}
template <class T> void Vec<T>::create(size_type n, const T& val)
{
	data=alloc.allocate(n,0);
	limit=avail=data+n;
	uninitialized_fill(data,limit,val);
}
template <class T> 
void Vec<T>::create(const_iterator i,const_iterator j)
{
	data=alloc.allocate(j-i,0);
	limit=avail=uninitialized_copy(i,j,data);
}
template <class T> void Vec<T>::uncreate()
{
	if(data)
	{
		//destroy (in reverse orde) the elements that were constructed
		iterator it=avail;
		while(it!=data)
			alloc.destroy(--it);

		//return all the space that was allocated
		alloc.deallocate(data,limit-data);
	}
	//reset pointers to indicate that the Vec is empty again
	data=limit=avail=0;
}
template <class T> void Vec<T>::grow()
{
	//when growing, allocate twice as much space as currently in use
	size_type new_size=_MAX(2*(limit-data),ptrdiff_t(1));

	//allocate new space and copy existing elements to the new space
	iterator new_data=alloc.allocate(new_size,0);
	iterator new_avail=uninitialized_copy(data,avail,new_data);

	//return the old space
	uncreate();

	//reset pointers to point to the newly allocate space
	data=new_data;
	avail=new_avail;
	limit=data+new_size;
}
template <class T> void Vec<T>::unchecked_append(const T& val)
{
	alloc.construct(avail++,val);
}
template <class T> Vec<T>::iterator Vec<T>::erase(iterator i)
{
	std::copy(i+1,avail,i);
	--avail;
	return i;
}
template <class T> void Vec<T>::clear()
{
	uncreate();
}
int main()
{
	Vec<int> v;
	for(Vec<int>::size_type i=0;i<10;++i)
		v.push_back(i+1);
	for(i=0;i<v.size();++i)
		cout<<v[i]<<endl;
	Vec<int> u(v);  
//	Vec<int> u(10,5); 
//	Vec<int> u=v;
	for(i=0;i<u.size();++i)
		cout<<u[i]<<string(3,' ');
	cout<<endl;
	u.erase(u.begin()+2);
	for(i=0;i<u.size();++i)
		cout<<u[i]<<string(3,' ');
	cout<<endl;
	u.clear();
	for(i=0;i<u.size();++i)
		cout<<u[i]<<string(3,' ');
	return 0;
}