reverse linked list

Author: k-capehart

2024/reverse_linked_list.py

@@ -0,0 +1,23 @@
+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 reverseList(self, head: Optional[ListNode]) -> Optional[ListNode]:
+        if not head or not head.next:
+            return head
+        return self.flipLinks(None, head)
+
+    def flipLinks(self, prev_node: Optional[ListNode], node: Optional[ListNode]) -> Optional[ListNode]:
+        if not node.next:
+            node.next = prev_node
+            return node
+        next_node = self.flipLinks(node, node.next)
+        node.next = prev_node
+        return next_node