re-solve "138. Copy List with Random Pointer"

src/copy_list_with_random_pointer.py

@@ -4,39 +4,34 @@
 class Node:
     def __init__(
         self, x: int, next: Node | None = None, random: Node | None = None
-    ):
+    ) -> None:
         self.val = int(x)
         self.next = next
         self.random = random
 
-    def __str__(self) -> str:
-        return f"Node({self.val})"
-
 
 class Solution:
     def copyRandomList(self, head: Node | None) -> Node | None:
-        new_dummy = Node(-1)
-        old_dummy = Node(-1, next=head)
+        old_to_new: dict[Node, Node] = {}
 
-        old_to_new: dict[Node | None, Node | None] = {None: None}
+        dummy = Node(-1)
 
-        new_current = new_dummy
-        old_current = old_dummy
+        old = head
+        new = dummy
 
-        while old_current.next:
-            old_current = old_current.next
-            new_node = Node(old_current.val)
-            new_current.next = new_node
-            new_current = new_current.next
+        while old:
+            node = Node(old.val, random=old.random)
+            new.next = node
+            new = node
 
-            old_to_new[old_current] = new_current
+            old_to_new[old] = node
+            old = old.next
 
-        new_current = new_dummy
-        old_current = old_dummy
+        current = dummy.next
 
-        while old_current.next and new_current.next:
-            old_current = old_current.next
-            new_current = new_current.next
-            new_current.random = old_to_new[old_current.random]
+        while current:
+            if current.random:
+                current.random = old_to_new[current.random]
+            current = current.next
 
-        return new_dummy.next
+        return dummy.next