feat: update generic data structures

.templates/leetcode/examples/linked_list.json5

@@ -41,8 +41,8 @@
     solution_methods: [
         {
             name: "reverse_between", // snake_case method name
-            parameters: "head: ListNode | None, left: int, right: int", // Use ListNode | None for nullable parameters
-            return_type: "ListNode | None", // Modern union syntax
+            parameters: "head: ListNode[int] | None, left: int, right: int", // Use ListNode[int] | None for nullable parameters
+            return_type: "ListNode[int] | None", // Modern union syntax with explicit generic type
             dummy_return: "None", // None for linked list problems
         },
     ],
@@ -65,14 +65,14 @@
             parametrize_typed: "head_list: list[int], left: int, right: int, expected_list: list[int]",
             test_cases: "[([1, 2, 3, 4, 5], 2, 4, [1, 4, 3, 2, 5]), ([5], 1, 1, [5])]",
             // IMPORTANT: Linked list test body converts arrays to ListNode and compares objects directly
-            body: "head = ListNode.from_list(head_list)\nexpected = ListNode.from_list(expected_list)\nresult = self.solution.reverse_between(head, left, right)\nassert result == expected",
+            body: "head = ListNode[int].from_list(head_list)\nexpected = ListNode[int].from_list(expected_list)\nresult = self.solution.reverse_between(head, left, right)\nassert result == expected",
         },
     ],
 
     // === PLAYGROUND NOTEBOOK ===
     // IMPORTANT: Linked list playground needs ListNode import and conversion
     playground_imports: "from solution import Solution\n\nfrom leetcode_py import ListNode",
-    playground_test_case: "# Example test case\nhead_list = [1, 2, 3, 4, 5]\nhead = ListNode.from_list(head_list)\nleft, right = 2, 4\nexpected = ListNode.from_list([1, 4, 3, 2, 5])",
+    playground_test_case: "# Example test case\nhead_list = [1, 2, 3, 4, 5]\nhead = ListNode[int].from_list(head_list)\nleft, right = 2, 4\nexpected = ListNode[int].from_list([1, 4, 3, 2, 5])",
     playground_execution: "result = Solution().reverse_between(head, left, right)\nresult",
     playground_assertion: "assert result == expected",
 }

.templates/leetcode/examples/tree.json5

@@ -45,8 +45,8 @@
     solution_methods: [
         {
             name: "invert_tree", // snake_case method name
-            parameters: "root: TreeNode | None", // Use TreeNode | None for nullable tree parameters
-            return_type: "TreeNode | None", // Modern union syntax (not Optional[TreeNode])
+            parameters: "root: TreeNode[int] | None", // Use TreeNode[int] | None for nullable tree parameters
+            return_type: "TreeNode[int] | None", // Modern union syntax with explicit generic type
             dummy_return: "None", // None for tree problems
         },
     ],
@@ -69,14 +69,14 @@
             parametrize_typed: "root_list: list[int | None], expected_list: list[int | None]",
             test_cases: "[([4, 2, 7, 1, 3, 6, 9], [4, 7, 2, 9, 6, 3, 1]), ([2, 1, 3], [2, 3, 1]), ([], [])]",
             // IMPORTANT: Tree test body converts arrays to TreeNode and compares objects directly
-            body: "root = TreeNode.from_list(root_list)\nexpected = TreeNode.from_list(expected_list)\nresult = self.solution.invert_tree(root)\nassert result == expected",
+            body: "root = TreeNode[int].from_list(root_list)\nexpected = TreeNode[int].from_list(expected_list)\nresult = self.solution.invert_tree(root)\nassert result == expected",
         },
     ],
 
     // === PLAYGROUND NOTEBOOK ===
     // IMPORTANT: Tree playground needs TreeNode import and conversion
     playground_imports: "from solution import Solution\n\nfrom leetcode_py import TreeNode",
-    playground_test_case: "# Example test case\nroot_list: list[int | None] = [4, 2, 7, 1, 3, 6, 9]\nroot = TreeNode.from_list(root_list)\nexpected = TreeNode.from_list([4, 7, 2, 9, 6, 3, 1])",
+    playground_test_case: "# Example test case\nroot_list: list[int | None] = [4, 2, 7, 1, 3, 6, 9]\nroot = TreeNode[int].from_list(root_list)\nexpected = TreeNode[int].from_list([4, 7, 2, 9, 6, 3, 1])",
     playground_execution: "result = Solution().invert_tree(root)\nresult",
     playground_assertion: "assert result == expected",
 }

.templates/leetcode/json/invert_binary_tree.json

@@ -18,8 +18,8 @@
     "solution_methods": [
         {
             "name": "invert_tree",
-            "parameters": "root: TreeNode | None",
-            "return_type": "TreeNode | None",
+            "parameters": "root: TreeNode[int] | None",
+            "return_type": "TreeNode[int] | None",
             "dummy_return": "None"
         }
     ],
@@ -34,11 +34,11 @@
             "parametrize": "root_list, expected_list",
             "parametrize_typed": "root_list: list[int | None], expected_list: list[int | None]",
             "test_cases": "[([4, 2, 7, 1, 3, 6, 9], [4, 7, 2, 9, 6, 3, 1]), ([2, 1, 3], [2, 3, 1]), ([], [])]",
-            "body": "root = TreeNode.from_list(root_list)\nexpected = TreeNode.from_list(expected_list)\nresult = self.solution.invert_tree(root)\nassert result == expected"
+            "body": "root = TreeNode[int].from_list(root_list)\nexpected = TreeNode[int].from_list(expected_list)\nresult = self.solution.invert_tree(root)\nassert result == expected"
         }
     ],
     "playground_imports": "from solution import Solution\n\nfrom leetcode_py import TreeNode",
-    "playground_test_case": "# Example test case\nroot_list: list[int | None] = [4, 2, 7, 1, 3, 6, 9]\nroot = TreeNode.from_list(root_list)\nexpected = TreeNode.from_list([4, 7, 2, 9, 6, 3, 1])",
+    "playground_test_case": "# Example test case\nroot_list: list[int | None] = [4, 2, 7, 1, 3, 6, 9]\nroot = TreeNode[int].from_list(root_list)\nexpected = TreeNode[int].from_list([4, 7, 2, 9, 6, 3, 1])",
     "playground_execution": "result = Solution().invert_tree(root)\nresult",
     "playground_assertion": "assert result == expected"
 }

.templates/leetcode/json/reverse_linked_list_ii.json

@@ -17,8 +17,8 @@
     "solution_methods": [
         {
             "name": "reverse_between",
-            "parameters": "head: ListNode | None, left: int, right: int",
-            "return_type": "ListNode | None",
+            "parameters": "head: ListNode[int] | None, left: int, right: int",
+            "return_type": "ListNode[int] | None",
             "dummy_return": "None"
         }
     ],
@@ -33,11 +33,11 @@
             "parametrize": "head_list, left, right, expected_list",
             "parametrize_typed": "head_list: list[int], left: int, right: int, expected_list: list[int]",
             "test_cases": "[([1, 2, 3, 4, 5], 2, 4, [1, 4, 3, 2, 5]), ([5], 1, 1, [5])]",
-            "body": "head = ListNode.from_list(head_list)\nexpected = ListNode.from_list(expected_list)\nresult = self.solution.reverse_between(head, left, right)\nassert result == expected"
+            "body": "head = ListNode[int].from_list(head_list)\nexpected = ListNode[int].from_list(expected_list)\nresult = self.solution.reverse_between(head, left, right)\nassert result == expected"
         }
     ],
     "playground_imports": "from solution import Solution\n\nfrom leetcode_py import ListNode",
-    "playground_test_case": "# Example test case\nhead_list = [1, 2, 3, 4, 5]\nhead = ListNode.from_list(head_list)\nleft, right = 2, 4\nexpected = ListNode.from_list([1, 4, 3, 2, 5])",
+    "playground_test_case": "# Example test case\nhead_list = [1, 2, 3, 4, 5]\nhead = ListNode[int].from_list(head_list)\nleft, right = 2, 4\nexpected = ListNode[int].from_list([1, 4, 3, 2, 5])",
     "playground_execution": "result = Solution().reverse_between(head, left, right)\nresult",
     "playground_assertion": "assert result == expected"
 }

leetcode/invert_binary_tree/playground.ipynb

@@ -14,7 +14,7 @@
    "id": "setup",
    "metadata": {},
    "outputs": [],
-   "source": ["# Example test case\nroot_list: list[int | None] = [4, 2, 7, 1, 3, 6, 9]\nroot = TreeNode.from_list(root_list)\nexpected = TreeNode.from_list([4, 7, 2, 9, 6, 3, 1])"]
+   "source": ["# Example test case\nroot_list: list[int | None] = [4, 2, 7, 1, 3, 6, 9]\nroot = TreeNode[int].from_list(root_list)\nexpected = TreeNode[int].from_list([4, 7, 2, 9, 6, 3, 1])"]
   },
   {
    "cell_type": "code",

leetcode/invert_binary_tree/solution.py

@@ -10,7 +10,7 @@ class Solution:
     # DFS recursive
     # Time: O(n)
     # Space: O(h) where h is height of tree
-    def invert_tree(self, root: TreeNode | None) -> TreeNode | None:
+    def invert_tree(self, root: TreeNode[int] | None) -> TreeNode[int] | None:
         if not root:
             return None
 
@@ -22,11 +22,11 @@ class SolutionDFS:
     # DFS iterative
     # Time: O(n)
     # Space: O(h) where h is height of tree
-    def invert_tree(self, root: TreeNode | None) -> TreeNode | None:
+    def invert_tree(self, root: TreeNode[int] | None) -> TreeNode[int] | None:
         if not root:
             return None
 
-        stack: list[TreeNode | None] = [root]
+        stack: list[TreeNode[int] | None] = [root]
         while stack:
             node = stack.pop()
             if node is None:
@@ -42,11 +42,11 @@ def invert_tree(self, root: TreeNode | None) -> TreeNode | None:
 class SolutionBFS:
     # Time: O(n)
     # Space: O(w) where w is maximum width of tree
-    def invert_tree(self, root: TreeNode | None) -> TreeNode | None:
+    def invert_tree(self, root: TreeNode[int] | None) -> TreeNode[int] | None:
         if not root:
             return None
 
-        queue: deque[TreeNode | None] = deque([root])
+        queue: deque[TreeNode[int] | None] = deque([root])
         while queue:
             node = queue.popleft()
             if node is None:

leetcode/invert_binary_tree/tests.py

@@ -20,7 +20,7 @@ def test_invert_tree(
         solution_class: type[Solution | SolutionDFS | SolutionBFS],
     ):
         solution = solution_class()
-        root = TreeNode.from_list(root_list)
-        expected = TreeNode.from_list(expected_list)
+        root = TreeNode[int].from_list(root_list)
+        expected = TreeNode[int].from_list(expected_list)
         result = solution.invert_tree(root)
         assert result == expected

leetcode/lru_cache/solution.py

@@ -3,7 +3,7 @@
 
 class LRUCache:
     # Space: O(capacity)
-    def __init__(self, capacity: int):
+    def __init__(self, capacity: int) -> None:
         self.capacity = capacity
         self.cache: OrderedDict[int, int] = OrderedDict()
 

leetcode/reverse_linked_list_ii/playground.ipynb

@@ -14,7 +14,7 @@
    "id": "setup",
    "metadata": {},
    "outputs": [],
-   "source": ["# Example test case\nhead_list = [1, 2, 3, 4, 5]\nhead = ListNode.from_list(head_list)\nleft, right = 2, 4\nexpected = ListNode.from_list([1, 4, 3, 2, 5])"]
+   "source": ["# Example test case\nhead_list = [1, 2, 3, 4, 5]\nhead = ListNode[int].from_list(head_list)\nleft, right = 2, 4\nexpected = ListNode[int].from_list([1, 4, 3, 2, 5])"]
   },
   {
    "cell_type": "code",

leetcode/reverse_linked_list_ii/solution.py

@@ -4,11 +4,11 @@
 class Solution:
     # Time: O(n)
     # Space: O(1)
-    def reverse_between(self, head: ListNode | None, left: int, right: int) -> ListNode | None:
+    def reverse_between(self, head: ListNode[int] | None, left: int, right: int) -> ListNode[int] | None:
         if not head or left == right:
             return head
 
-        dummy = ListNode(0)
+        dummy = ListNode[int](0)
         dummy.next = head
         prev = dummy
 

leetcode/reverse_linked_list_ii/tests.py

@@ -18,7 +18,7 @@ def setup_method(self):
     def test_reverse_between(
         self, head_list: list[int], left: int, right: int, expected_list: list[int]
     ):
-        head = ListNode.from_list(head_list)
-        expected = ListNode.from_list(expected_list)
+        head = ListNode[int].from_list(head_list)
+        expected = ListNode[int].from_list(expected_list)
         result = self.solution.reverse_between(head, left, right)
         assert result == expected

leetcode_py/data_structures/list_node.py

@@ -1,10 +1,16 @@
-class ListNode:
-    def __init__(self, val: int = 0, next: "ListNode | None" = None):
+from typing import Generic, TypeVar
+
+# TODO: Remove TypeVar when minimum Python version is 3.12+ (use class ListNode[T]: syntax)
+T = TypeVar("T")
+
+
+class ListNode(Generic[T]):
+    def __init__(self, val: T, next: "ListNode[T] | None" = None):
         self.val = val
         self.next = next
 
     @classmethod
-    def from_list(cls, arr: list[int]) -> "ListNode | None":
+    def from_list(cls, arr: list[T]) -> "ListNode[T] | None":
         if not arr:
             return None
         head = cls(arr[0])
@@ -14,9 +20,9 @@ def from_list(cls, arr: list[int]) -> "ListNode | None":
             current = current.next
         return head
 
-    def to_list(self) -> list[int]:
+    def to_list(self) -> list[T]:
         result = []
-        current: "ListNode | None" = self
+        current: "ListNode[T] | None" = self
         while current:
             result.append(current.val)
             current = current.next

leetcode_py/data_structures/tree_node.py

@@ -1,8 +1,13 @@
+from typing import Any, Generic, TypeVar
+
 import graphviz
 from anytree import Node, RenderTree
 
+# TODO: Remove TypeVar when minimum Python version is 3.12+ (use class TreeNode[T]: syntax)
+T = TypeVar("T")
+
 
-def build_anytree(node: "TreeNode | None", parent: Node | None = None) -> Node | None:
+def build_anytree(node: "TreeNode[Any] | None", parent: Node | None = None) -> Node | None:
     if not node:
         return Node("None", parent=parent) if parent else None
     current = Node(str(node.val), parent=parent)
@@ -12,7 +17,7 @@ def build_anytree(node: "TreeNode | None", parent: Node | None = None) -> Node |
     return current
 
 
-def add_nodes(dot: graphviz.Digraph, node: "TreeNode | None", node_id: int = 0) -> int:
+def add_nodes(dot: graphviz.Digraph, node: "TreeNode[Any] | None", node_id: int = 0) -> int:
     if not node:
         return node_id
 
@@ -31,14 +36,14 @@ def add_nodes(dot: graphviz.Digraph, node: "TreeNode | None", node_id: int = 0)
     return next_id - 1
 
 
-class TreeNode:
-    def __init__(self, val: int = 0, left: "TreeNode | None" = None, right: "TreeNode | None" = None):
+class TreeNode(Generic[T]):
+    def __init__(self, val: T, left: "TreeNode[T] | None" = None, right: "TreeNode[T] | None" = None):
         self.val = val
         self.left = left
         self.right = right
 
     @classmethod
-    def from_list(cls, arr: list[int | None]) -> "TreeNode | None":
+    def from_list(cls, arr: list[T | None]) -> "TreeNode[T] | None":
         """Convert array representation to binary tree."""
         if not arr or arr[0] is None:
             return None
@@ -66,10 +71,10 @@ def from_list(cls, arr: list[int | None]) -> "TreeNode | None":
 
         return root
 
-    def to_list(self) -> list[int | None]:
+    def to_list(self) -> list[T | None]:
         """Convert binary tree to array representation."""
-        result: list[int | None] = []
-        queue: list[TreeNode | None] = [self]
+        result: list[T | None] = []
+        queue: list[TreeNode[T] | None] = [self]
 
         while queue:
             node = queue.pop(0)