206. 反转链表

题目链接：https://leetcode.cn/problems/reverse-linked-list/
难度：简单

描述：
给你单链表的头节点 head ，请你反转链表，并返回反转后的链表。

题解

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:
    def reverseList(self, head: ListNode) -> ListNode:
        pre = None
        cur = head
        while cur is not None:
            temp = cur.next
            cur.next = pre
            pre = cur
            cur = temp
        return pre