feat(content): function signatures + test cases

backend/data/questions/count-good-nodes-in-binary-tree.yaml

@@ -9,6 +9,30 @@ patterns:
   - dfs
   - tree-traversal
 
+function_signature: "def good_nodes(root: TreeNode) -> int:"
+
+test_cases:
+  visible:
+    - input: { root: [3, 1, 4, 3, null, 1, 5] }
+      expected: 4
+    - input: { root: [3, 3, null, 4, 2] }
+      expected: 3
+    - input: { root: [1] }
+      expected: 1
+  hidden:
+    - input: { root: [2, 2, 2] }
+      expected: 3
+    - input: { root: [5, 4, 3, 2, 1] }
+      expected: 1
+    - input: { root: [1, 2, 3, 4, 5, 6, 7] }
+      expected: 7
+    - input: { root: [-1, -2, -3, -4, -5] }
+      expected: 1
+    - input: { root: [10, 5, 15, 3, 7, 12, 20] }
+      expected: 4
+    - input: { root: [9, 3, 10, null, 6, 9, 14, 4, 8] }
+      expected: 4
+
 description: |
   Given a binary tree `root`, a node *X* in the tree is named **good** if in the path from root to *X* there are no nodes with a value *greater than* X.