feat(content): function signatures + test cases

backend/data/questions/all-nodes-distance-k-in-binary-tree.yaml

@@ -11,6 +11,26 @@ patterns:
   - bfs
   - dfs
 
+function_signature: "def distance_k(root: TreeNode, target: TreeNode, k: int) -> list[int]:"
+
+test_cases:
+  visible:
+    - input: { root: [3, 5, 1, 6, 2, null, 8, null, null, 7, 4], target: 5, k: 2 }
+      expected: [7, 4, 1]
+    - input: { root: [1], target: 1, k: 3 }
+      expected: []
+  hidden:
+    - input: { root: [0, 1, null, 3, 2], target: 2, k: 1 }
+      expected: [1]
+    - input: { root: [0, 1, 2], target: 0, k: 1 }
+      expected: [1, 2]
+    - input: { root: [0, 1, 2], target: 0, k: 0 }
+      expected: [0]
+    - input: { root: [3, 5, 1, 6, 2, 0, 8, null, null, 7, 4], target: 3, k: 1 }
+      expected: [5, 1]
+    - input: { root: [1, 2, 3, 4], target: 4, k: 2 }
+      expected: [1]
+
 description: |
   Given the `root` of a binary tree, the value of a target node `target`, and an integer `k`, return *an array of the values of all nodes that have a distance* `k` *from the target node*.