feat(content): function signatures + test cases

backend/data/questions/check-if-matrix-is-x-matrix.yaml

@@ -9,6 +9,24 @@ categories:
 patterns:
   - matrix-traversal
 
+function_signature: "def check_x_matrix(grid: list[list[int]]) -> bool:"
+
+test_cases:
+  visible:
+    - input: { grid: [[2, 0, 0, 1], [0, 3, 1, 0], [0, 5, 2, 0], [4, 0, 0, 2]] }
+      expected: true
+    - input: { grid: [[5, 7, 0], [0, 3, 1], [0, 5, 0]] }
+      expected: false
+  hidden:
+    - input: { grid: [[1, 0, 1], [0, 1, 0], [1, 0, 1]] }
+      expected: true
+    - input: { grid: [[1, 0, 0], [0, 1, 0], [0, 0, 1]] }
+      expected: false
+    - input: { grid: [[0, 0, 1], [0, 1, 0], [1, 0, 0]] }
+      expected: false
+    - input: { grid: [[5, 0, 5], [0, 5, 0], [5, 0, 5]] }
+      expected: true
+
 description: |
   A square matrix is said to be an **X-Matrix** if **both** of the following conditions hold: