06.从尾到头打印链表

2021-08-24

题目

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

来源：力扣（LeetCode） 链接：https://leetcode-cn.com/problems/cong-wei-dao-tou-da-yin-lian-biao-lcof 著作权归领扣网络所有。商业转载请联系官方授权，非商业转载请注明出处。

JS实现

1、reverse()方法，反转数组

/**
 * Definition for singly-linked list.
 * function ListNode(val) {
 *     this.val = val;
 *     this.next = null;
 * }
 */
/**
 * @param {ListNode} head
 * @return {number[]}
 */
var reversePrint = function(head) {
  const result = [];
  let current = head;
  while(current){
    result.push(current.val);
    current = current.next;
  }
  return result.reverse();
};

2、借助栈

var reversePrint = function(head) {
  const result = [];

  const stack = [];
  let current = head;
  while(current){
    stack.push(current.val);
    current = current.next;
  }

  while(stack.length){
    result.push(stack.pop());
  }

  return result;
};

3、unshift()方法，在数组开头插入元素

var reversePrint = function(head) {
  const result = [];
  let current = head;
  while(current){
    result.unshift(current.val);
    current = current.next;
  }
  return result;
};