public bool IsSymmetric(TreeNode root)
{
bool ok;
if (root == null)
{
return true;
}
ok = Rec(root.left, root.right);
return ok;
}
public static bool Rec(TreeNode one, TreeNode two)
{
if (one == null && two == null)
{
return true;
}
else if (one == null || two == null)
{
return false;
}
else if (one.val != two.val)
{
return false;
}
bool ok = Rec(one.left, two.right)
&& Rec(one.right, two.left);
return ok;
}