leetcode.com 61. Rotate List

문제 링크: https://leetcode.com/problems/rotate-list

Author: skysign

leetcode.com 61. Rotate List/main.py

@@ -0,0 +1,42 @@
+from typing import Optional
+
+
+# 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]:
+        # linked list length is 1
+        if head is None or head.next is None:
+            return head
+
+        length = 0
+        node = head
+        while node:
+            length += 1
+            node = node.next
+
+        k = k % length
+
+        # from here, linked list length is 2 at least
+        for _ in range(k):
+            tail = self.get_tail(head)
+            tail.next = head
+            head = tail
+
+        return head
+
+    def get_tail(self, node: Optional[ListNode]):
+        prev = node
+        node = node.next
+
+        while node.next:
+            prev = node
+            node = node.next
+
+        prev.next = None
+        return node