package com.wang.code.one;

/**

* @author WANGJJ

* @date 2020/04/23

*/

import java.util.Iterator;

import java.util.NoSuchElementException;

import java.util.Scanner;

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

private int N;

private Node<Item> first;

private static class Node<Item> {

private Item item;

private Node<Item> next;

}

public Bag() {

first = null;

N = 0;

}

public boolean isEmpty() {

return first == null;

}

public int size() {

return N;

}

public void add(Item item) {

Node<Item> oldfirst = first;

first = new Node<Item>();

first.item = item;

first.next = oldfirst;

N ++;

}

@Override

public Iterator<Item> iterator() {

return new ListIterator<Item>(first);

}

private class ListIterator<Item> implements Iterator<Item> {

private Node<Item> current;

public ListIterator(Node<Item> first) {

current = first;

}

@Override

public boolean hasNext() { return current != null; }

@Override

public void remove() { throw new UnsupportedOperationException(); }

@Override

public Item next() {

if(!hasNext()) {

throw new NoSuchElementException();

}

Item item = current.item;

current = current.next;

return item;

}

}

public static void main(String[] args) {

Bag<String> bag = new Bag<String>();

Scanner in = new Scanner(System.in);

int n = in.nextInt();

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

String item = in.next();

bag.add(item);

}

System.out.println("size of bag = " + bag.size());

for(String s : bag) {

System.out.println(s);

}

for (String s : bag) {

System.out.println(s);

}

}

}