/*

* Sample usage: java ResizingArrayStack < tobe.txt

*/

import java.util.Iterator;

public class ResizingArrayStack<Item> implements Iterable<Item> {

private Item[] a = (Item[]) new Object[1]; //stack entries

private int N; // size

public boolean isEmpty(){

return N==0;

}

public int size(){

return N;

}

private void resize(int max){

// Move stack to a new array os size max.

Item[] temp = (Item[]) new Object[max];

for (int i = 0; i < N; i++){

temp[i] = a[i];

}

a = temp;

}

public void push(Item item){

// Add item to top of the stack

if (N == a.length){

resize(2*a.length);

}

a[N] = item;

N++;

}

public Item pop(){

// Remove item from top of the stack

N--;

Item item = a[N];

a[N] = null; // Avoid loitering

if (N > 0 && N == a.length/4){

resize(a.length/2);

}

return item;

}

public Iterator<Item> iterator(){

return new ReverseArrayIterator();

}

private class ReverseArrayIterator implements Iterator<Item>{

// Support LIFO iteration

private int i = N;

public boolean hasNext(){

return i > 0;

}

public Item next(){

i--;

return a[i];

}

public void remove(){ }

}

public static void main(String[] args){

ResizingArrayStack<String> s;

s = new ResizingArrayStack<String>();

while (!StdIn.isEmpty()){

String item = StdIn.readString();

if (!item.equals("-")){

s.push(item);

}

else if (!item.isEmpty()){

StdOut.print(s.pop()+" ");

}

}

StdOut.println("("+s.size()+" left in stack)");

}

}