题解 | #链表内指定区间反转#

# 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
# @param m int整型
# @param n int整型
# @return ListNode类
#
class Solution:
    def reverseBetween(self, head: ListNode, m: int, n: int) -> ListNode:
        res = pre = ListNode(0)
        res.next = cur = head
        for _ in range(1,m):
            pre = cur
            cur = cur.next
        for _ in range(m,n):
            tmp = cur.next
            cur.next = tmp.next
            tmp.next = pre.next
            pre.next = tmp
        return res.next