feat(content): hidden test cases

backend/data/questions/construct-quad-tree.yaml

@@ -11,6 +11,24 @@ patterns:
   - matrix-traversal
   - dfs
 
+function_signature: "def construct(grid: list[list[int]]) -> Node:"
+
+test_cases:
+  visible:
+    - input: { grid: [[0, 1], [1, 0]] }
+      expected: [[0, 1], [1, 0], [1, 1], [1, 1], [1, 0]]
+    - input: { grid: [[1, 1], [1, 1]] }
+      expected: [[1, 1]]
+  hidden:
+    - input: { grid: [[0]] }
+      expected: [[1, 0]]
+    - input: { grid: [[1]] }
+      expected: [[1, 1]]
+    - input: { grid: [[0, 0], [0, 0]] }
+      expected: [[1, 0]]
+    - input: { grid: [[1, 1, 0, 0], [1, 1, 0, 0], [0, 0, 1, 1], [0, 0, 1, 1]] }
+      expected: [[0, 1], [1, 1], [1, 0], [1, 0], [1, 1]]
+
 description: |
   Given a `n * n` matrix `grid` of `0`s and `1`s only. We want to represent `grid` with a Quad-Tree.