CIQ48のフィギュアを10体売る

問題： https://codeiq.jp/ace/joboffer_apli/q677

クエリ式とメソッド形式を混ぜるのは、邪道なんだろうな。

Program.cs

using System;
using System.Collections.Generic;
using System.Linq;

class Program
{
    static void Main(string[] args)
    {
        var priceList = new[] { 0, 1, 6, 8, 10, 17, 18, 20, 24, 26, 30 };
        var all = Partition(10, 10, List.Empty).Select(x => x.AsEnumerable());
        var descending =
            from l in all
            orderby l.Select(x => priceList[x]).Sum() descending
            select l;
        Console.WriteLine(string.Join(",", descending.First()));
    }

    static IEnumerable<List> Partition(int number, int max, List list)
    {
        if (number == 0)
        {
            return Enumerable.Repeat<List>(list, 1);
        }
        return
            from i in Enumerable.Range(1, Math.Min(max, number))
            from c in Partition(number - i, i, list.Add(i))
            select c;
    }
}

class List
{
    public readonly int? Head;
    public readonly List Tail;
    private List(int? head, List tail)
    {
        this.Head = head;
        this.Tail = tail;
    }
    public static readonly List Empty = new List(null, null);
    public List Add(int head)
    {
        return new List(head, this);
    }
    public IEnumerable<int> AsEnumerable()
    {
        for (var i = this; i != List.Empty; i = i.Tail)
        {
            yield return i.Head.Value;
        }
    }
}