题解 | #链表内指定区间反转#

多练习，多练习，多练习

class Solution:
    def reverseBetween(self , head: ListNode, m: int, n: int) -> ListNode:
        # write code here
        p = ListNode(0)   # 保证p.next 存在
        p.next = head
        new_head = p
        cur = None
        i = 1
        while i < n:
            if i < m:
                p = head
                head = head.next
            elif i >= m:
                cur = head.next
                head.next = cur.next  # 这样可以保证不丢掉第n个节点之后的节点
                cur.next = p.next
                p.next = cur
            i += 1
        return new_head.next