feat(content): function signatures + test cases

backend/data/questions/lemonade-change.yaml

@@ -8,6 +8,28 @@ categories:
 patterns:
   - greedy
 
+function_signature: "def lemonade_change(bills: list[int]) -> bool:"
+
+test_cases:
+  visible:
+    - input: { bills: [5, 5, 5, 10, 20] }
+      expected: true
+    - input: { bills: [5, 5, 10, 10, 20] }
+      expected: false
+  hidden:
+    - input: { bills: [5] }
+      expected: true
+    - input: { bills: [10] }
+      expected: false
+    - input: { bills: [5, 5, 10] }
+      expected: true
+    - input: { bills: [5, 5, 5, 5, 20, 20] }
+      expected: true
+    - input: { bills: [5, 5, 5, 10, 5, 20, 5, 10, 5, 20] }
+      expected: true
+    - input: { bills: [5, 5, 10, 20, 5, 5, 5, 5, 5, 5, 5, 5, 5, 10, 5, 5, 20, 5, 20, 5] }
+      expected: true
+
 description: |
   At a lemonade stand, each lemonade costs `$5`. Customers are standing in a queue to buy from you and order one at a time (in the order specified by `bills`). Each customer will only buy one lemonade and pay with either a `$5`, `$10`, or `$20` bill. You must provide the correct change to each customer so that the net transaction is that the customer pays `$5`.