题解 | 链表内指定区间反转

#感觉写的很烧脑啊，应该有更简单的写法吧
#在head前面加个ph， p1指向上一个node，p指向当前，p1初始值ph ， p初始值head,i为下标初始为1
#i<m是逐步后移，m n 之间是普通反转， 等于m或n时特殊处理
等于m时， 记录当时的 pm ， pm1 
等于n时， pm1.next = p
         pm.next = p.next
         p.next = p1




# 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
        i = 1
        p = head
        p1 = None
        ph = ListNode(1)
        ph.next = head
        p1= ph 
        while p and  i<=n:
            if i<m :
                p1= p
                p = p.next
            elif i==m:
                pm = p
                pm1 = p1
                p1=p
                p = p.next
            elif i>m and i<n:
                tmp = p.next 
                p.next = p1
                p1=p
                p = tmp
            elif i==n:
                pm1.next = p
                pm.next = p.next
                tmp = p.next 
                p.next = p1
                p1 = pm
                p = tmp
            i +=1
        return ph.next





   
     

###还是人家的写法妙啊，每次就调整指向的那一位的位置
#{3,5,6,7,9,0},1,5
#[-1, 5, 3, 6, 7, 9, 0]
#[-1, 6, 5, 3, 7, 9, 0]
#[-1, 7, 6, 5, 3, 9, 0]
#[-1, 9, 7, 6, 5, 3, 0]
#
from os import curdir
# 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
        res = ListNode(-1)
        res.next = head
        pre = res
        cur = head
        for i in range(1,m):
            pre = cur
            cur = cur.next
        for i in range(m,n):
            temp = cur.next
            cur.next = temp.next
            temp.next = pre.next
            pre.next = temp
            # p  =res
            # l = []
            # while p:
            #     l.append(p.val)
            #     p= p.next
            # print(l)
        return res.next