feat(content): function signatures + test cases

backend/data/questions/binary-tree-maximum-path-sum.yaml

@@ -11,6 +11,28 @@ patterns:
   - dfs
   - dynamic-programming
 
+function_signature: "def max_path_sum(root: TreeNode) -> int:"
+
+test_cases:
+  visible:
+    - input: { root: [1, 2, 3] }
+      expected: 6
+    - input: { root: [-10, 9, 20, null, null, 15, 7] }
+      expected: 42
+  hidden:
+    - input: { root: [1] }
+      expected: 1
+    - input: { root: [-3] }
+      expected: -3
+    - input: { root: [2, -1] }
+      expected: 2
+    - input: { root: [-2, -1] }
+      expected: -1
+    - input: { root: [5, 4, 8, 11, null, 13, 4, 7, 2, null, null, null, 1] }
+      expected: 48
+    - input: { root: [1, -2, -3, 1, 3, -2, null, -1] }
+      expected: 3
+
 description: |
   A **path** in a binary tree is a sequence of nodes where each pair of adjacent nodes in the sequence has an edge connecting them. A node can only appear in the sequence **at most once**. Note that the path does not need to pass through the root.