feat(content): more test cases

backend/data/questions/kth-smallest-element-in-a-bst.yaml

@@ -10,6 +10,24 @@ patterns:
   - dfs
   - tree-traversal
 
+function_signature: "def kth_smallest(root: TreeNode | None, k: int) -> int:"
+
+test_cases:
+  visible:
+    - input: { root: [3, 1, 4, null, 2], k: 1 }
+      expected: 1
+    - input: { root: [5, 3, 6, 2, 4, null, null, 1], k: 3 }
+      expected: 3
+    - input: { root: [1], k: 1 }
+      expected: 1
+  hidden:
+    - input: { root: [2, 1, 3], k: 2 }
+      expected: 2
+    - input: { root: [5, 3, 6, 2, 4, null, null, 1], k: 6 }
+      expected: 6
+    - input: { root: [3, 1, 4, null, 2], k: 4 }
+      expected: 4
+
 description: |
   Given the `root` of a binary search tree, and an integer `k`, return the `k`<sup>th</sup> smallest value (**1-indexed**) of all the values of the nodes in the tree.