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
        if head==None or head.next==None:return head
        late = n-m

        pi = head
        for _ in range(late):pi = pi.next
        pj = head
        dummy_head = ListNode(0)
        dummy_head.next = head
        prej = dummy_head

        for _ in range(m-1):
            pi = pi.next
            pj = pj.next
            prej = prej.next
           

        #反转
        nexti = pi.next
        pre,p = pj,pj.next

        while(p!=nexti):
            tmp = p
            p = p.next
            tmp.next = pre
            pre = tmp
        prej.next = pi
        pj.next = nexti
        return dummy_head.next

指定区间翻转，本来以为挺简单就能搞定，但是其实发现有很多细节的地方没注意就会报错，比如边界条件的处理，然后要做一个假头，后面的指针比前面的多走多少步，后面又应该一起走多少步，然后最后翻转的这个操作怎么写才不会错，然后就是debug要快……