struct my_arr{
	int *start ;
	int *begin ;
	int *end ;
	my_arr(){
		start = new int;
		begin = start;
		end = start;
	}
	~my_arr(){
		delete start;
		cout << "my_arr已被~"<<endl; 
	}
	int top(){
		return *end;
	}
	int head(){
		return *begin;
	}
	void push(int n){
		end ++;
		*end = n;
	}
	void pop(){
		*end = 0;
		end --;
	}
	bool empty(){
		if(start == end) return true;
		else return false;
	}
}s;