LeetCode 206. 反转链表

题目

反转一个单链表。

示例:

输入: 1->2->3->4->5->NULL
输出: 5->4->3->2->1->NULL

进阶:
你可以迭代或递归地反转链表。你能否用两种方法解决这道题？

解题思路

记录一个数组值，然后再遍历重新赋值

class Solution:
    def reverseList(self, head: ListNode) -> ListNode:
        tempList = []
        tempHead = head
        while tempHead != None:
            tempList.append(tempHead.val)
            tempHead = tempHead.next
        res = head
        while len(tempList)>0:
            res.val = tempList.pop()
            res = res.next
        return head

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution:
    def reverseList(self, head: ListNode) -> ListNode:
        #正统做法
        pre = None
        cur = head
        while cur != None:
            tempNode = cur.next
            cur.next = pre
            pre = cur
            cur = tempNode
        return pre