feat(content): function signatures + test cases

backend/data/questions/add-one-row-to-tree.yaml

@@ -12,6 +12,24 @@ patterns:
   - dfs
   - tree-traversal
 
+function_signature: "def add_one_row(root: TreeNode, val: int, depth: int) -> TreeNode:"
+
+test_cases:
+  visible:
+    - input: { root: [4, 2, 6, 3, 1, 5], val: 1, depth: 2 }
+      expected: [4, 1, 1, 2, null, null, 6, 3, 1, 5]
+    - input: { root: [4, 2, null, 3, 1], val: 1, depth: 3 }
+      expected: [4, 2, null, 1, 1, 3, null, null, 1]
+  hidden:
+    - input: { root: [1], val: 2, depth: 1 }
+      expected: [2, 1]
+    - input: { root: [1, 2, 3], val: 5, depth: 2 }
+      expected: [1, 5, 5, 2, null, null, 3]
+    - input: { root: [1], val: 2, depth: 2 }
+      expected: [1, 2, 2]
+    - input: { root: [4, 2, 6, 3, 1, 5], val: 1, depth: 1 }
+      expected: [1, 4, null, 2, 6, 3, 1, 5]
+
 description: |
   Given the `root` of a binary tree and two integers `val` and `depth`, add a row of nodes with value `val` at the given depth `depth`.