LeetCode 筆記 - 61. Rotate List

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:
    def rotateRight(self, head: Optional[ListNode], k: int) -> Optional[ListNode]:
        
        size = 0
        current_node = end = head
        while current_node:
            end = current_node
            current_node = current_node.next
            size += 1
        
        if size <= 1:
            return head
        
        k %= size
        if k == 0:
            return head
        
        current_node = head
        for _ in range(size - k - 1):
            current_node = current_node.next
        
        new_head = current_node.next
        current_node.next = None
        end.next = head
        
        return new_head