feat(content): function signatures + test cases

backend/data/questions/construct-binary-tree-from-preorder-and-inorder-traversal.yaml

@@ -11,6 +11,26 @@ patterns:
   - dfs
   - tree-traversal
 
+function_signature: "def build_tree(preorder: list[int], inorder: list[int]) -> TreeNode | None:"
+
+test_cases:
+  visible:
+    - input: { preorder: [3, 9, 20, 15, 7], inorder: [9, 3, 15, 20, 7] }
+      expected: [3, 9, 20, null, null, 15, 7]
+    - input: { preorder: [-1], inorder: [-1] }
+      expected: [-1]
+  hidden:
+    - input: { preorder: [1, 2], inorder: [2, 1] }
+      expected: [1, 2]
+    - input: { preorder: [1, 2], inorder: [1, 2] }
+      expected: [1, null, 2]
+    - input: { preorder: [1, 2, 3], inorder: [2, 1, 3] }
+      expected: [1, 2, 3]
+    - input: { preorder: [1, 2, 4, 5, 3, 6, 7], inorder: [4, 2, 5, 1, 6, 3, 7] }
+      expected: [1, 2, 3, 4, 5, 6, 7]
+    - input: { preorder: [5, 4, 3, 2, 1], inorder: [1, 2, 3, 4, 5] }
+      expected: [5, 4, null, 3, null, 2, null, 1]
+
 description: |
   Given two integer arrays `preorder` and `inorder` where `preorder` is the preorder traversal of a binary tree and `inorder` is the inorder traversal of the same tree, construct and return *the binary tree*.