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Author: NinePiece2

Solutions/0061-rotate-list/README.md

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+<p>Given the <code>head</code> of a linked&nbsp;list, rotate the list to the right by <code>k</code> places.</p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+<img alt="" src="https://assets.leetcode.com/uploads/2020/11/13/rotate1.jpg" style="width: 450px; height: 191px;" />
+<pre>
+<strong>Input:</strong> head = [1,2,3,4,5], k = 2
+<strong>Output:</strong> [4,5,1,2,3]
+</pre>
+
+<p><strong class="example">Example 2:</strong></p>
+<img alt="" src="https://assets.leetcode.com/uploads/2020/11/13/roate2.jpg" style="width: 305px; height: 350px;" />
+<pre>
+<strong>Input:</strong> head = [0,1,2], k = 4
+<strong>Output:</strong> [2,0,1]
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li>The number of nodes in the list is in the range <code>[0, 500]</code>.</li>
+	<li><code>-100 &lt;= Node.val &lt;= 100</code></li>
+	<li><code>0 &lt;= k &lt;= 2 * 10<sup>9</sup></code></li>
+</ul>

Solutions/0061-rotate-list/solution.py

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+# 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]:
+        if head is None or head.next is None:
+            return head
+        
+        current, n = head, 0
+        while current:
+            n += 1
+            current = current.next
+        
+        k %= n
+        if k == 0:
+            return head
+        
+        fast = slow = head
+        for _ in range(k):
+            fast = fast.next
+        while fast.next:
+            fast, slow = fast.next, slow.next
+        
+        result = slow.next
+        slow.next = None
+        fast.next = head
+        return result