feat(content): more test cases

backend/data/questions/diameter-of-binary-tree.yaml

@@ -10,6 +10,26 @@ patterns:
   - dfs
   - tree-traversal
 
+function_signature: "def diameter_of_binary_tree(root: TreeNode) -> int:"
+
+test_cases:
+  visible:
+    - input: { root: [1, 2, 3, 4, 5] }
+      expected: 3
+    - input: { root: [1, 2] }
+      expected: 1
+  hidden:
+    - input: { root: [1] }
+      expected: 0
+    - input: { root: [1, 2, 3] }
+      expected: 2
+    - input: { root: [1, 2, null, 3, null, 4] }
+      expected: 3
+    - input: { root: [1, 2, 3, 4, 5, 6, 7] }
+      expected: 4
+    - input: { root: [4, -7, -3, null, null, -9, -3, 9, -7, -4, null, 6, null, -6, -6, null, null, 0, 6, 5, null, 9, null, null, -1, -4, null, null, null, -2] }
+      expected: 8
+
 description: |
   Given the `root` of a binary tree, return *the length of the **diameter** of the tree*.