feat(content): function signatures + test cases

backend/data/questions/delete-node-in-a-bst.yaml

@@ -9,6 +9,30 @@ patterns:
   - tree-traversal
   - dfs
 
+function_signature: "def delete_node(root: TreeNode | None, key: int) -> TreeNode | None:"
+
+test_cases:
+  visible:
+    - input: { root: [5, 3, 6, 2, 4, null, 7], key: 3 }
+      expected: [5, 4, 6, 2, null, null, 7]
+    - input: { root: [5, 3, 6, 2, 4, null, 7], key: 0 }
+      expected: [5, 3, 6, 2, 4, null, 7]
+    - input: { root: [], key: 0 }
+      expected: []
+  hidden:
+    - input: { root: [5], key: 5 }
+      expected: []
+    - input: { root: [5, 3, 7], key: 5 }
+      expected: [7, 3]
+    - input: { root: [5, 3, 7, 2, 4, 6, 8], key: 3 }
+      expected: [5, 4, 7, 2, null, 6, 8]
+    - input: { root: [5, 3, 7, 2, 4, 6, 8], key: 7 }
+      expected: [5, 3, 8, 2, 4, 6]
+    - input: { root: [2, 1, 3], key: 1 }
+      expected: [2, null, 3]
+    - input: { root: [50, 30, 70, 20, 40, 60, 80], key: 50 }
+      expected: [60, 30, 70, 20, 40, null, 80]
+
 description: |
   Given a root node reference of a BST and a key, delete the node with the given key in the BST. Return *the **root node reference** (possibly updated) of the BST*.