http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=ALDS1_11_B

DFS.cs

<Query Kind="Program">
  <Reference>&lt;RuntimeDirectory&gt;\System.dll</Reference>
  <Reference>&lt;RuntimeDirectory&gt;\System.Net.dll</Reference>
  <Reference>&lt;RuntimeDirectory&gt;\System.Net.Http.dll</Reference>
  <Reference>&lt;RuntimeDirectory&gt;\System.Web.dll</Reference>
  <NuGetReference>Microsoft.Net.Http</NuGetReference>
  <NuGetReference>Newtonsoft.Json</NuGetReference>
  <NuGetReference>Sendgrid</NuGetReference>
  <Namespace>Newtonsoft.Json</Namespace>
  <Namespace>Newtonsoft.Json.Bson</Namespace>
  <Namespace>Newtonsoft.Json.Converters</Namespace>
  <Namespace>Newtonsoft.Json.Linq</Namespace>
  <Namespace>Newtonsoft.Json.Schema</Namespace>
  <Namespace>Newtonsoft.Json.Serialization</Namespace>
  <Namespace>SendGrid.SmtpApi</Namespace>
  <Namespace>System.IO</Namespace>
  <Namespace>System.Net</Namespace>
  <Namespace>System.Web.Mail</Namespace>
</Query>
// 提出用using
//using System;
//using System.Linq;
//using System.Collections.Generic;
public class DFS
{
	public static void Main()
	{
		var n = int.Parse(Console.ReadLine());
		var u = Enumerable.Range(0, n)
			.Select(_ => Console.ReadLine());
		
		var builtupNodes = Build(u);
		var explorer = new Explorer();
		while (builtupNodes.Any(x => x.FoundTime == 0))
		{
			explorer.Explore(builtupNodes.First(x => x.FoundTime == 0));
		}
		
		// 出力用 ForEach用にToList()
		builtupNodes.ToList()
			.ForEach(x => Console.WriteLine(x.Id + " " + x.FoundTime + " " + x.FinishedTime));
	}
	
	static IEnumerable<Node> Build(IEnumerable<string> u)
	{
		var nodeAndInputs = u.Select(x => x.Split(' '))
			.Select(x => x.Select(int.Parse))
			.Select(x => new 
			{ 
				node = new Node(x.First()),
				input = x
			})
			.ToList();
		// Nodeを一旦つくってから子供を入れている。ループ2回回しててあんまりうまくないです。
		return nodeAndInputs.Select(nodeinput => 
		{
			nodeinput.node.Children = nodeAndInputs
				.Select(x => x.node)
				.Where(x => nodeinput.input.Skip(2).Contains(x.Id));
			return nodeinput.node;
		})
		.OrderBy(x => x.Id);
	}
	
	class Explorer
	{
		private int time = 0;
		public void Explore(Node node)
		{
			node.FoundTime = ++time;
			node.Children.ToList().ForEach(x => { if (x.FoundTime == 0) Explore(x); });
			node.FinishedTime = ++time;
		}
	}
	
	class Node
	{
		public int Id { get; private set; }
		public IEnumerable<Node> Children { get; set; }
		public int FoundTime { get; set; }
		public int FinishedTime { get; set; }
		
		public Node(int id) { Id = id; }
	}
}