void InternalTest(int?[] tree, int p, int q, TreeNode expected)
{
TreeNode root = TreeNode.Get(tree);
TreeNode nodeP = new TreeNode(p);
TreeNode nodeQ = new TreeNode(q);
TreeNode actual = LowestCommonAncestor.Solve(root, nodeP, nodeQ);
Assert.Equal <int>(expected.val, actual.val);
}