feat(content): function signatures + test cases

backend/data/questions/delete-leaves-with-a-given-value.yaml

@@ -10,6 +10,30 @@ patterns:
   - dfs
   - tree-traversal
 
+function_signature: "def remove_leaf_nodes(root: TreeNode | None, target: int) -> TreeNode | None:"
+
+test_cases:
+  visible:
+    - input: { root: [1, 2, 3, 2, null, 2, 4], target: 2 }
+      expected: [1, null, 3, null, 4]
+    - input: { root: [1, 3, 3, 3, 2], target: 3 }
+      expected: [1, 3, null, null, 2]
+    - input: { root: [1, 2, null, 2, null, 2], target: 2 }
+      expected: [1]
+  hidden:
+    - input: { root: [2], target: 2 }
+      expected: []
+    - input: { root: [1], target: 2 }
+      expected: [1]
+    - input: { root: [1, 1, 1], target: 1 }
+      expected: []
+    - input: { root: [5, 3, 7, 2, 4, 6, 8], target: 9 }
+      expected: [5, 3, 7, 2, 4, 6, 8]
+    - input: { root: [1, 2, 3, 4, 2, 2, 5], target: 2 }
+      expected: [1, 2, 3, 4, null, null, 5]
+    - input: { root: [3, 3, 3, 3, 3, 3, 3], target: 3 }
+      expected: []
+
 description: |
   Given a binary tree `root` and an integer `target`, delete all the **leaf nodes** with value `target`.