剑指 Offer 06. 从尾到头打印链表

输入一个链表的头节点，从尾到头反过来返回每个节点的值（用数组返回）。

示例 1：

输入：head = [1,3,2]
输出：[2,3,1]

限制：

0 <= 链表长度 <= 10000

 方法一:

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public int[] reversePrint(ListNode head) {
        ListNode temp = head;
        int length = 0;
        while(temp != null){
            length++;
            temp = temp.next;
        } 

        int[] ls = new int[length];
        for(int i=ls.length-1;i>=0;i--){
            ls[i] = head.val;
            head = head.next;
            if(head == null){
                break;
            }
        }
        return ls;
    }
}

 

  方法二:使用栈:

   

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
import java.util.*;
class Solution {
    public int[] reversePrint(ListNode head) {
        Stack<ListNode> stack = new Stack<>();
        while(head!=null){
            stack.add(head);
            head = head.next;
        }
        int[] ls = new int[stack.size()];
        for(int i=0;i<ls.length;i++){
            ls[i] = stack.pop().val;
        }
        return ls;
    }
}