3 从尾到头打印链表

题目描述

输入一个链表，从尾到头打印链表每个节点的值。

 

 

思路1：stack

 

import java.util.ArrayList;
import java.util.Stack;
public class Solution {
    public ArrayList<Integer> printListFromTailToHead(ListNode listNode) {
        Stack<Integer> s=new Stack<Integer>();
        for(ListNode l = listNode;l!=null;l=l.next)
            s.push(l.val);
        ArrayList<Integer> newlist = new ArrayList<Integer>();
        while(!s.isEmpty()){
            newlist.add(s.pop());
        }
        return newlist;
    }

import java.util.ArrayList;
import java.util.Stack;
public class Solution {
    public ArrayList<Integer> printListFromTailToHead(ListNode head) {
        Stack<Integer>  s = new Stack<Integer>();
        for(;head!=null;head = head.next)
            s.push(head.val);
        ArrayList<Integer> list = new ArrayList<Integer>();
        for( int item : s)
            list.add(item);
         return list;
    }
}

迭代返回的是无序的！！！！！！！！

20180303

# -*- coding:utf-8 -*-
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution:
    # 返回从尾部到头部的列表值序列，例如[1,2,3]
    def printListFromTailToHead(self, root):
        # write code here
        res = []
        while root!=None:
            res.append(root.val)
            root = root.next
        return res[::-1]