校招准备系列：每天一道算法题（12）-从尾到头打印链表

从尾到头打印链表

public class Solution {
ArrayList<Integer> arrayList=new ArrayList<Integer>();
public ArrayList<Integer> printListFromTailToHead(ListNode listNode) {
if(listNode!=null){
this.printListFromTailToHead(listNode.next);
arrayList.add(listNode.val);
}
return arrayList;
}
}

/**
*    public class ListNode {
*        int val;
*        ListNode next = null;
*
*        ListNode(int val) {
*            this.val = val;
*        }
*    }
*
*/
import java.util.ArrayList;
public class Solution {
public ArrayList<Integer> printListFromTailToHead(ListNode listNode) {
ArrayList<Integer> list = new ArrayList<Integer>();
ListNode pre = null;
ListNode next = null;
while(listNode!=null){
next = listNode.next;
listNode.next = pre;
pre = listNode;
listNode = next;
}
while(pre!=null){
list.add(pre.val);
pre = pre.next;
}
return list;
}
}

import java.util.ArrayList;
import java.util.Collections;
public class Solution {
public ArrayList<Integer> printListFromTailToHead(ListNode listNode) {
ArrayList<Integer> list = new ArrayList<Integer>();

while(listNode != null){
list.add(listNode.val);
listNode = listNode.next;
}

Collections.reverse(list);//使用Collections的reverse方法，直接将list反转
return list;
}
}