feat(content): more test cases

backend/data/questions/maximum-depth-of-binary-tree.yaml

@@ -11,6 +11,24 @@ patterns:
   - bfs
   - tree-traversal
 
+function_signature: "def max_depth(root: TreeNode | None) -> int:"
+
+test_cases:
+  visible:
+    - input: { root: [3, 9, 20, null, null, 15, 7] }
+      expected: 3
+    - input: { root: [1, null, 2] }
+      expected: 2
+    - input: { root: [] }
+      expected: 0
+  hidden:
+    - input: { root: [1] }
+      expected: 1
+    - input: { root: [1, 2, 3, 4, 5] }
+      expected: 3
+    - input: { root: [1, 2, null, 3, null, 4] }
+      expected: 4
+
 description: |
   Given the `root` of a binary tree, return *its maximum depth*.