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
        dummy = ListNode(-1)
        dummy.next = head
        p0 = dummy
        for i in range(m-1):
            p0 = p0.next 
        cur = p0.next
        pre = None 
        for i in range(n-m+1):
            nxt = cur.next
            cur.next = pre
            pre = cur 
            cur = nxt
        p0.next.next = cur 
        p0.next = pre 
        return dummy.next 

将链表内指定区间看作一个整体，对该区间翻转，随后连接头节点和尾节点。