//CIS:610-251 Data Structures and Algos
//Assignment # 2 Question # 1
//Stack Operations

#include<iostream.h>

class Stack
{
private:
	int  * data; //data value in stack
	unsigned sp;      // Stack Pointer
	unsigned spMax;   //Max Stack Pointer Value;
public:
	Stack() ;
	Stack(Stack& s);
	Stack(unsigned size); 
	
	void push(int);
	int pop() ;
	int StackTop();
	bool Empty(void);
	
};

//Constructor
Stack::Stack()
{ 
	data=new int(256);	//init data as an array of 256 integer
	sp=0;				//Stack initialized
	spMax=255;			
	data[0]=NULL;		
}

//Constructor if size of Stack is given
Stack::Stack(unsigned size)
{ 
	sp=0;
	spMax=size;
	data=new int(size+1);
	data[0]=NULL;
}

//Copy Constructor
Stack::Stack(Stack& s)
{
	unsigned i=1;
	this->sp=s.sp;
	this->spMax=s.spMax;
	this->data=new int[this->spMax+1];
	for(;i<=sp;i++) this->data[i]=s.data[i];
	
}

//Empty
bool Stack::Empty(void)
{
	if (sp) return false ; 
	else return true;
	
}

//Add an element to Stack and increment the SP.
void Stack::push(int item)
{ 
	 data[++sp]=item; 
		
}

//Return the Top most element of stack and decrement the SP
int Stack::pop()
{ 
	return data[sp--]; 
	
}

//return how many elements in Stack.
int Stack::StackTop()
{
	return data[sp];
}




main()
{
Stack main;
int i=0,n=3;

main.push(2);
main.push(9);
main.push(7);
main.push(3);
main.push(50);
main.push(44);
main.push(13);

//a
	if (!main.Empty()) main.pop();
	if (!main.Empty()) i=main.pop(); 
	cout << "Second Item from Top = " << i;
//b
	Stack temp1(main);
	if (!temp1.Empty()) temp1.pop();
	if (!temp1.Empty()) i=temp1.pop(); 
	cout << "\nSecond Item from Top = " << i;
//c
	for(i=1;i<n;i++) main.pop();
	i=main.pop();
	cout << "\nFor n=3, item = " << i;
//d
	main.push(7);
	main.push(3);
	main.push(50);
	Stack temp2(main);
	for(i=1;i<n;i++) temp2.pop();
	i=temp2.pop();
	cout << "\nFor n=3, item = " << i;
//e
	while (!main.Empty()) i=main.pop();
	cout << "\nBottom Most item = " << i;
//f
	main.push(2);
	main.push(9);
	main.push(7);
	main.push(3);
	Stack temp3(main);
	while (!temp3.Empty()) i=temp3.pop();
	cout << "\nBottom Most item = " << i;
//g
	int i1=0,i2=0,i3=0;
	while(!main.Empty())
	{
		i1=i2;i2=i3;i3=main.pop();
	}
	cout << "\nThird item from bottom = " << i1 << '\n';

return 0;
}