题解 | #链表内指定区间反转#

from pickle import NONE
from re import template
# 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:
        # write code here
        def reverseList(pre, cur, nxt, k):
            for i in range(k):
                cur.next = nxt.next
                nxt.next = pre.next
                pre.next = nxt
                # 步骤顺序不可调换
                nxt = cur.next
        
        temp = ListNode(0)
        temp.next = head
        pre = temp
        cur = head
        nxt = head.next
        for i in range(m-1):
            pre = cur
            cur = nxt
            nxt = nxt.next
        reverseList(pre, cur, nxt, n-m)
        return temp.next