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:
        # write code here
        pre = ListNode(-1)
        pre.next = head
        
        fast = head
        slow = pre
        for i in range(m-1):
            slow = fast
            fast = fast.next
        for j in range(n-m):
            temp = fast.next
            fast.next = temp.next
            temp.next = slow.next
            slow.next = temp
            
        return pre.next