rotate_linked_list.py

from collections import deque


# Definition for singly-linked list.
class ListNode:
    def __init__(self, val=0, next=None):
        self.val = val
        self.next = next


# Definition for singly-linked list.
class ListNode(object):
    def __init__(self, val=0, next=None):
        self.val = val
        self.next = next

def rotateRight(head, k):
    if not head or k == 0:
        return head

    length = 1
    tail = head
    while tail.next:
        tail = tail.next
        length += 1

    k = k % length
    if k == 0:
        return head

    tail.next = head  # Make it circular
    steps_to_new_head = length - k
    new_tail = tail
    while steps_to_new_head:
        new_tail = new_tail.next
        steps_to_new_head -= 1

    new_head = new_tail.next
    new_tail.next = None
    return new_head


print(rotateRight())