从尾到头打印链表

【题目】输入一个链表的头节点，从尾到头反过来打印每个节点的值。

1. 遍历的顺序是从头到尾，打印的顺序则是从尾到头，首先，想到栈，然后，递归的本质是一个栈结构，因此，想到用递归。

import java.util.Stack;

public class Main {

    Stack<Node> stack = new Stack<Node>();

    public static void main(String[] args) {

        Node node4 = new Node(4, null);
        Node node3 = new Node(3, node4);
        Node node2 = new Node(2, node3);
        Node node1 = new Node(1, node2);
        Node node0 = new Node(0, node1);

        Main main = new Main();

        main.process(node0);
        main.process2(node0);

    }

    // 递归实现
    public void process(Node head) {

        if (null != head) {

            if (null != head.next) {
                process(head.next);
            }

            System.out.print(head.value + " ");
        }
    }

    // 栈实现
    public void process2(Node head) {

        Node p = head;

        while (null != p) {
            stack.add(p);
            p = p.next;
        }

        while (!stack.isEmpty()) {
            System.out.print(stack.pop().value + " ");
        }
    }
}

class Node {
    int value;
    Node next;

    public Node(int value, Node nextNode) {
        this.value = value;
        this.next = nextNode;
    }
}