feat(content): function signatures + test cases

backend/data/questions/bus-routes.yaml

@@ -10,6 +10,28 @@ categories:
 patterns:
   - bfs
 
+function_signature: "def num_buses_to_destination(routes: list[list[int]], source: int, target: int) -> int:"
+
+test_cases:
+  visible:
+    - input: { routes: [[1, 2, 7], [3, 6, 7]], source: 1, target: 6 }
+      expected: 2
+    - input: { routes: [[7, 12], [4, 5, 15], [6], [15, 19], [9, 12, 13]], source: 15, target: 12 }
+      expected: -1
+  hidden:
+    - input: { routes: [[1, 2, 3]], source: 1, target: 1 }
+      expected: 0
+    - input: { routes: [[1, 2, 3]], source: 1, target: 3 }
+      expected: 1
+    - input: { routes: [[1, 2], [2, 3], [3, 4]], source: 1, target: 4 }
+      expected: 3
+    - input: { routes: [[1, 5], [5, 10], [10, 20]], source: 1, target: 20 }
+      expected: 3
+    - input: { routes: [[1, 2, 3], [4, 5, 6]], source: 1, target: 6 }
+      expected: -1
+    - input: { routes: [[1, 2, 3, 4, 5]], source: 1, target: 5 }
+      expected: 1
+
 description: |
   You are given an array `routes` representing bus routes where `routes[i]` is a bus route that the i<sup>th</sup> bus repeats forever.