feat(content): more test cases

backend/data/questions/combinations.yaml

@@ -9,6 +9,22 @@ categories:
 patterns:
   - backtracking
 
+function_signature: "def combine(n: int, k: int) -> list[list[int]]:"
+
+test_cases:
+  visible:
+    - input: { n: 4, k: 2 }
+      expected: [[1, 2], [1, 3], [1, 4], [2, 3], [2, 4], [3, 4]]
+    - input: { n: 1, k: 1 }
+      expected: [[1]]
+  hidden:
+    - input: { n: 5, k: 3 }
+      expected: [[1, 2, 3], [1, 2, 4], [1, 2, 5], [1, 3, 4], [1, 3, 5], [1, 4, 5], [2, 3, 4], [2, 3, 5], [2, 4, 5], [3, 4, 5]]
+    - input: { n: 3, k: 1 }
+      expected: [[1], [2], [3]]
+    - input: { n: 2, k: 2 }
+      expected: [[1, 2]]
+
 description: |
   Given two integers `n` and `k`, return *all possible combinations of* `k` *numbers chosen from the range* `[1, n]`.