using System;

using System.Collections.Generic;

public class Program

{

    public class Person {

      public string Name {get; set;}

      public Person Father {get; set;}

      public Person Mother {get; set;}

​

      public Person () {}

      public Person (string name, Person father, Person mother) {

            this.Name = name;

            this.Mother = mother;

            this.Father = father;

      }

    }

    public static void Main()

    {

        var pebbles = new Person {

                                   Name="Pebbles", 

                                   Father=new Person { Name="Fred",

                                                       Father=new Person { Name="Ed",

                                                                           Father=new Person { Name="Jim",

                                                                                               Father=new Person { Name="Jack",

                                                                                                                   Father=new Person { Name="Bo",

                                                                                                                                       Father=new Person { Name="Eutacious", Father=null, Mother=null }, Mother=null },

                                                                                                                   Mother=null },

                                                                                               Mother=null },

                                                                           Mother=null },

                                                       Mother=new Person { Name="Edna", Father=null, Mother=null } },

                                   Mother=new Person { Name="Wilma", 

                                                       Father=null,

                                                       Mother=new Person { Name="Pearl", Father=null, Mother=null }

                                   }

                                 };

​

        List<string> names = getNamesOfAllAncestors(pebbles);

        // should print [Pebbles, Fred, Ed, Jim, Jack, Bo, Edna, Wilma, Pearl]

        System.Console.WriteLine("[{0}]", string.Join(", ", names));

        names = getNamesOfAllAncestors(person:pebbles, maxRecurseLevel:1, includeAnalytics:true);

        // should print [Pebbles, Fred, Wilma]

        System.Console.WriteLine("[{0}]", string.Join(", ", names));

    }

    // implement me

    public static List<string> getNamesOfAllAncestors(Person person, int recurseLevel=0, int? maxRecurseLevel=null, bool includeAnalytics=false) {

        List<string> ancestors = new List<string>();

​

        if ((maxRecurseLevel != null) && (recurseLevel > maxRecurseLevel.Value)) {

            return ancestors;           

        }

        ancestors.Add(person.Name + (includeAnalytics?("{" + recurseLevel + "}"):"") );

​

        if(person.Father != null){

            ancestors.AddRange(getNamesOfAllAncestors(person.Father, recurseLevel+1, maxRecurseLevel, includeAnalytics));

        }

​

        if(person.Mother != null){

            ancestors.AddRange(getNamesOfAllAncestors(person.Mother, recurseLevel+1, maxRecurseLevel, includeAnalytics));

        }

​

        return ancestors;

    }

}