feat(content): function signatures + test cases

backend/data/questions/binary-tree-cameras.yaml

@@ -10,6 +10,26 @@ patterns:
   - dfs
   - greedy
 
+function_signature: "def min_camera_cover(root: TreeNode) -> int:"
+
+test_cases:
+  visible:
+    - input: { root: [0, 0, null, 0, 0] }
+      expected: 1
+    - input: { root: [0, 0, null, 0, null, 0, null, null, 0] }
+      expected: 2
+  hidden:
+    - input: { root: [0] }
+      expected: 1
+    - input: { root: [0, 0] }
+      expected: 1
+    - input: { root: [0, 0, 0] }
+      expected: 1
+    - input: { root: [0, 0, 0, 0, 0, 0, 0] }
+      expected: 2
+    - input: { root: [0, 0, null, 0, null, 0, null, 0] }
+      expected: 2
+
 description: |
   You are given the `root` of a binary tree. We install cameras on the tree nodes where each camera at a node can monitor its parent, itself, and its immediate children.