面试题5: 从尾到头打印链表

一. 题目

输入一个链表的头结点,从尾到头反过来打印出每个节点的值.

代码请到我的代码库中下载 Point2Offer

二. 代码

package com;import java.util.Stack;/** * 剑指offer: 从尾到头输出列表 * 两种考虑:1.不改变链表结构(栈,递归);2.改变链表结构(遍历/递归,见链表反转,这里不考虑) * 测试用例三种(链表有多个节点,一个节点核链表为空) * @author dingding * Date:2017-6-14 15:06 * Declaration: All Rights Reserved! */public class PrintReversedList {    public static void main(String[] args) {        test3();        test2();        test1();    }    //方法1: 使用栈    private static void printByStack(ListNode pHead){        Stack<Integer> list = new Stack<Integer>();        if (pHead==null) {            System.out.println("空链表");        }else{            while (pHead!=null){                list.push((Integer)pHead.getValue());                pHead = pHead.getNext();            }            while (!list.isEmpty()){                Integer a = list.pop();                System.out.print(a+" ");            }            System.out.println();        }    }    //方法2:使用递归    private static void printByRecursive(ListNode pHead){        if (pHead!=null) {            if (pHead.getNext()!=null){                printByRecursive(pHead.getNext());            }            System.out.print(pHead.getValue()+" ");   //若放在46行,结果会出错        }else{            System.out.println("空链表!");        }    }    //打印链表    private static void printList(ListNode first) {        if (first==null) {            System.out.println("空链表!");        }else{            while (first!=null){                System.out.print(first.getValue()+" ");                first = first.getNext();            }            System.out.println();        }    }    //===========测试用例===============    private static void test(ListNode first){        System.out.println("初始链表:");        printList(first);        System.out.println("使用栈从尾到头打印链表:");        printByStack(first);        System.out.println("递归从尾到头打印链表:");        printByRecursive(first);        System.out.println();    }    //链表有多个节点    private static void test3() {        ListNode first = new ListNode(1);        ListNode second = new ListNode(2);        ListNode third = new ListNode(3);        ListNode fourth = new ListNode(4);        first.setNext(second);        second.setNext(third);        third.setNext(fourth);        test(first);        System.out.println("=============================");    }    //链表只有一个节点    private static void test2() {        ListNode first = new ListNode(1);        test(first);        System.out.println("=============================");    }    //链表为空    private static void test1() {        test(null);    }}

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有不妥当之处,麻烦告知:D