题解 | 反转链表

# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None
#
# 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
#
# 
# @param head ListNode类 
# @return ListNode类
#
class Solution:
    def ReverseList(self , head: ListNode) -> ListNode:
        # write code here
        prev = None
        curr = head
        next = None

        while curr:
            next = curr.next  # 临时保存

            curr.next = prev   # 指针指向前一个值

            prev = curr   # prev往右边挪一位
            curr = next   # curr往右边挪一位
        
        if prev:
            return prev