Find path from root to a target node in Binary Tree

        def root_to_target(root: TreeNode, target: int):
            path = []

            def dfs(node):
                if not node:
                    return False

                path.append(node.val)

                if node.val == target:
                    return True

                if dfs(node.left) or dfs(node.right):
                    return True

                path.pop()      # backtrack
                return False

            if dfs(root):
                return path
            return []