算法4学习-1.3.3.8 下压(LIFO)栈(链表实现)

上一篇的链表实现

代码

import java.util.Iterator;

/**
 * 下压(LIFO)栈(链表实现)
 * 
 * Created by tuzhis on 2016年1月14日.
 */
public class ReSizingArrayStack<Item> implements Iterable<Item> {

    private Node first; // 栈顶(最近添加的元素)
    private int N; // 元素数量

    private class Node {
        Item item;
        Node next;
    }

    public boolean isEmpty() {
        return first == null;
    }

    public int size() {
        return N;
    }

    public void push(Item item) {
        Node oldfirst = first;
        first = new Node();
        first.item = item;
        first.next = oldfirst;
        N++;
    }

    public Item pop() {
        Item item = first.item;
        first = first.next;
        N--;
        return item;
    }

    @Override
    public Iterator<Item> iterator() {
        return new ListIterator();
    }

    private class ListIterator implements Iterator<Item> {
        private Node current = first;

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

        @Override
        public Item next() {
            Item item = current.item;
            current = current.next;
            return item;
        }
    }

}