feat(content): more test cases

backend/data/questions/add-two-numbers.yaml

@@ -9,6 +9,22 @@ categories:
 patterns:
   - two-pointers
 
+function_signature: "def add_two_numbers(l1: ListNode | None, l2: ListNode | None) -> ListNode | None:"
+
+test_cases:
+  visible:
+    - input: { l1: [2, 4, 3], l2: [5, 6, 4] }
+      expected: [7, 0, 8]
+    - input: { l1: [0], l2: [0] }
+      expected: [0]
+    - input: { l1: [9, 9, 9, 9, 9, 9, 9], l2: [9, 9, 9, 9] }
+      expected: [8, 9, 9, 9, 0, 0, 0, 1]
+  hidden:
+    - input: { l1: [1], l2: [9, 9] }
+      expected: [0, 0, 1]
+    - input: { l1: [5], l2: [5] }
+      expected: [0, 1]
+
 description: |
   You are given two **non-empty** linked lists representing two non-negative integers. The digits are stored in **reverse order**, and each of their nodes contains a single digit. Add the two numbers and return the sum as a linked list.