feat(content): function signatures + test cases

backend/data/questions/beautiful-arrangement.yaml

@@ -9,6 +9,26 @@ categories:
 patterns:
   - backtracking
 
+function_signature: "def count_arrangement(n: int) -> int:"
+
+test_cases:
+  visible:
+    - input: { n: 2 }
+      expected: 2
+    - input: { n: 1 }
+      expected: 1
+  hidden:
+    - input: { n: 3 }
+      expected: 3
+    - input: { n: 4 }
+      expected: 8
+    - input: { n: 5 }
+      expected: 10
+    - input: { n: 6 }
+      expected: 36
+    - input: { n: 10 }
+      expected: 700
+
 description: |
   Suppose you have `n` integers labelled `1` through `n`. A permutation of those `n` integers `perm` (**1-indexed**) is considered a **beautiful arrangement** if for every `i` (`1 <= i <= n`), **either** of the following is true: