using System;
using System.Collections;
class Stack
{
private ArrayList array;
public Stack()
{
array = new ArrayList();
}
static void Main(string[] args)
{
Stack s = new Stack();
s.Push(10);
s.Push(16);
s.Push(100);
s.Pop();
s.printStack();
}
public int? Peek()
{
if (array.Count > 0)
return (int)array[array.Count - 1]; //end / last / latest added
return null;
}
public void Push(int value)
{
array.Add(value);
}
public int? Pop()
{
if (array.Count == 0)
{
return null;
}
int lastItem = (int)array[array.Count - 1];
array.RemoveAt(array.Count - 1);
return lastItem;
}
public void printStack()
{
for(int i = array.Count - 1; i >= 0 ; i--) //foreach index from top, write array item and go down
{
Console.WriteLine(array[i]);
}
}
}
