92、反转链表（中等）

class Solution:
    def reverseBetween(self, head: ListNode, left: int, right: int) -> ListNode:
        prev = None
        curr = head
        next = head
        for i in range(left-1):
            prev = curr
            curr = curr.next
        prev2 = prev
        curr2 = curr

        for i in range(right - left +1):
            next = curr.next
            curr.next = prev
            prev = curr
            curr = next

        if prev2 != None:
            prev2.next = prev
        else:
            head = prev

        curr2.next = curr

        return head

61 旋转链表(中等)

class Solution:
    def rotateRight(self, head: Optional[ListNode], k: int) -> Optional[ListNode]:
        if head == None or head.next == None or k == 0:
            return head
        len = 1 
        curr = head
        while curr.next:
            len += 1
            curr = curr.next
        k %=len
        if k== 0:
            return head
        temp = head
        for i in range(len - k -1):
            temp = temp.next
        
        new_head = temp.next
        curr.next = head
        temp.next = None
        return new_head

143、重排链表

class Solution:
    def reorderList(self, head: ListNode) -> None:
        """
        Do not return anything, modify head in-place instead.
        """
        if not head:
            return head

        temp  = []
        while head:
            temp.append(head)
            head = head.next

        for i in range(len(temp)//2):
            temp[i].next = temp[~i]
            temp[~i].next = temp[i+1]
        temp[len(temp)//2].next = None
        return temp[0]