feat(content): function signatures + test cases

backend/data/questions/4sum-ii.yaml

@@ -9,6 +9,24 @@ categories:
 patterns:
   - two-pointers
 
+function_signature: "def four_sum_count(nums1: list[int], nums2: list[int], nums3: list[int], nums4: list[int]) -> int:"
+
+test_cases:
+  visible:
+    - input: { nums1: [1, 2], nums2: [-2, -1], nums3: [-1, 2], nums4: [0, 2] }
+      expected: 2
+    - input: { nums1: [0], nums2: [0], nums3: [0], nums4: [0] }
+      expected: 1
+  hidden:
+    - input: { nums1: [-1, -1], nums2: [-1, 1], nums3: [-1, 1], nums4: [1, -1] }
+      expected: 6
+    - input: { nums1: [1], nums2: [-1], nums3: [0], nums4: [0] }
+      expected: 1
+    - input: { nums1: [0, 1, -1], nums2: [-1, 1, 0], nums3: [0, 0, 1], nums4: [-1, 1, 1] }
+      expected: 17
+    - input: { nums1: [1, 1, 1], nums2: [1, 1, 1], nums3: [-1, -1, -1], nums4: [-1, -1, -1] }
+      expected: 81
+
 description: |
   Given four integer arrays `nums1`, `nums2`, `nums3`, and `nums4` all of length `n`, return the number of tuples `(i, j, k, l)` such that: