feat(content): function signatures + test cases

backend/data/questions/check-if-n-and-its-double-exist.yaml

@@ -9,6 +9,28 @@ categories:
 patterns:
   - two-pointers
 
+function_signature: "def check_if_exist(arr: list[int]) -> bool:"
+
+test_cases:
+  visible:
+    - input: { arr: [10, 2, 5, 3] }
+      expected: true
+    - input: { arr: [3, 1, 7, 11] }
+      expected: false
+    - input: { arr: [7, 1, 14, 11] }
+      expected: true
+  hidden:
+    - input: { arr: [0, 0] }
+      expected: true
+    - input: { arr: [-2, 0, 10, -19, 4, 6, -8] }
+      expected: false
+    - input: { arr: [-10, 12, -20, -8, 15] }
+      expected: true
+    - input: { arr: [1, 2, 3, 4] }
+      expected: true
+    - input: { arr: [1, 3, 5, 7] }
+      expected: false
+
 description: |
   Given an array `arr` of integers, check if there exist two indices `i` and `j` such that: