输入一个链表，从尾到头打印链表每个节点的值。
思路：首先借助一个栈，遍历链表中的每一个值，然后存储到栈中，利用栈的先进后出特点，然后添加到数组中返回。
package demo3;
import java.util.ArrayList;
import java.util.Stack;
public class Main {
static class ListNode{
int val;
ListNode next = null;
ListNode(int val){
this.val = val;
}
}
public static void main(String[] args) {
ListNode node1 = new ListNode(1);
ListNode node2 = new ListNode(2);
ListNode node3 = new ListNode(3);
node1.next = node2;
node2.next=node3;
node3.next = null;
ArrayList result = printListFromTailToHead(node1);
print(result);
}
public static void print(ArrayList result){
if (result != null && result.size()>0) {
for (int i=0;i<result.size();i++) {
System.out.print(result.get(i)+" ");
}
System.out.println();
}
}
public static ArrayList printListFromTailToHead(ListNode listNode){
ArrayList array = new ArrayList();
//借助栈
Stack stack = new Stack();
if (listNode == null) {
return array;
}
while (listNode != null) {//节点不为空
stack.push(listNode.val);
listNode = listNode.next;
}
while (!stack.isEmpty()) {
array.add(stack.pop());
}
return array;
}
}