public static void Test() { Solution s = new Solution(); int?[] t1 = new int?[] { 1, 2, 3, null, 4, null, 5 }; TreeNode root = new TreeNode(t1[0].GetValueOrDefault()); ProduceTreeNode(t1, t1.Length, 0, root); Console.WriteLine(s.IsCousins(root, 5, 3)); }