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
        current = head
        while current:
            next_node = current.next  # 保存下一个节点
            current.next = prev  # 反转当前节点的指针
            prev = current  # 移动prev到当前节点
            current = next_node  # 移动current到下一个节点
        return prev  # 返回新的头节点