feat(content): function signatures + test cases

backend/data/questions/all-possible-full-binary-trees.yaml

@@ -11,6 +11,26 @@ patterns:
   - backtracking
   - dynamic-programming
 
+function_signature: "def all_possible_fbt(n: int) -> list[TreeNode]:"
+
+test_cases:
+  visible:
+    - input: { n: 7 }
+      expected: 5
+    - input: { n: 3 }
+      expected: 1
+  hidden:
+    - input: { n: 1 }
+      expected: 1
+    - input: { n: 2 }
+      expected: 0
+    - input: { n: 5 }
+      expected: 2
+    - input: { n: 9 }
+      expected: 14
+    - input: { n: 4 }
+      expected: 0
+
 description: |
   Given an integer `n`, return *a list of all possible **full binary trees** with* `n` *nodes*. Each node of each tree in the answer must have `Node.val == 0`.