feat(content): function signatures + test cases

backend/data/questions/check-completeness-of-a-binary-tree.yaml

@@ -9,6 +9,30 @@ patterns:
   - bfs
   - tree-traversal
 
+function_signature: "def is_complete_tree(root: TreeNode) -> bool:"
+
+test_cases:
+  visible:
+    - input: { root: [1, 2, 3, 4, 5, 6] }
+      expected: true
+    - input: { root: [1, 2, 3, 4, 5, null, 7] }
+      expected: false
+  hidden:
+    - input: { root: [1] }
+      expected: true
+    - input: { root: [1, 2] }
+      expected: true
+    - input: { root: [1, null, 2] }
+      expected: false
+    - input: { root: [1, 2, 3, 4, 5, 6, 7] }
+      expected: true
+    - input: { root: [1, 2, 3, 4, null, 6, 7] }
+      expected: false
+    - input: { root: [1, 2, 3, null, null, 6, 7] }
+      expected: false
+    - input: { root: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] }
+      expected: true
+
 description: |
   Given the `root` of a binary tree, determine if it is a *complete binary tree*.