using System;

using System.Linq;

​

public class Node

{

    public static Node Fail = new Node { Val = null, Next = null };

    public static Node Nil = new Node { Val = null, Next = null };

    public string Val { get; private set; }

    public Node Next { get; private set; }

    private Node() { }

    public Node(string val, Node next) { Val = val; Next = next ?? Nil; }

    public static Func<Node, Node> InitQuery() { return (node) => node; }

}

​

public static class NodeExtensions

{

    public static Node ToDomainNodes(this string target)

    {

        return target

            .Split('.')

            .Aggregate(Node.Nil, (node, dom) => new Node(dom, node));

​

    }

​

    public static Func<Node, Node> ThenMatch(this Func<Node, Node> target, string val)

    {

        return (node) =>

        {

            var firstResult = target(node);

​

            if (firstResult != Node.Fail)

                return (firstResult == Node.Fail || firstResult == Node.Nil || firstResult.Val != val)

                    ? Node.Fail

                    : firstResult.Next;

​

            return firstResult;

        };

    }

​

    public static bool IsSubdomainOf(this string fqdn, string domain)

    {

        return domain

            .Split('.')

            .Reverse()

            .Aggregate(Node.InitQuery(), (query, domainPart) => query.ThenMatch(domainPart))

            (fqdn.ToDomainNodes()) != Node.Fail;

    }

}

​

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

        Console.WriteLine("foo.bar.baz.example.com".IsSubdomainOf("baz.example.com"));

        Console.ReadLine();

    }

}