Inverse Fizzbuzz (FizzBuzzの逆関数) #C#

（追記）もっと簡潔になるように解き直しました。→ http://qiita.com/items/6a0774443413c71c09d9

問題は http://d.hatena.ne.jp/matarillo/20120515/p1

私の答えは、範囲内の解をすべてリストアップしています。

解が1つでよい場合は、offsetsと掛け合わせずに、shortestsの先頭の配列だけ返せばよいです。
そうすれば、メソッドの引数からstartとendを削除できます。

Program.cs

using System;
using System.Linq;
using E = System.Linq.Enumerable;

class Program
{
    static void Main()
    {
        var result = InverseFizzBuzz(new[] { "fizz", "fizz", "buzz" }, 1, 100);
        foreach (var a in result)
        {
            Console.WriteLine(string.Join(",", a));
        }
    }

    static Tuple<int,string>[] table = E.Zip(
        new[] { 0, 3, 5, 6, 9, 10, 12},
        new[] { "fizzbuzz", "fizz", "buzz", "fizz", "fizz", "buzz", "fizz" },
        (x, y) => Tuple.Create(x, y)).ToArray();

    static int FromIndex(int index)
    {
        return (index / 7 * 15) + table[index % 7].Item1;
    }

    static bool IsMatch(int index, string value)
    {
        return table[index % 7].Item2 == value;
    }

    static int[][] InverseFizzBuzz(string[] input, int start, int end)
    {
        var list = from index in E.Range(0, 7)
                   let indices = E.Range(index, input.Length)
                   let tuples = E.Zip(indices, input, (x, y) => Tuple.Create(x, y))
                   where tuples.All(x => IsMatch(x.Item1, x.Item2))
                   let rStart = FromIndex(tuples.First().Item1)
                   let rEnd = FromIndex(tuples.Last().Item1)
                   select E.Range(rStart, rEnd - rStart + 1).ToArray();

        var lookup = list
            .Select(x => new { Value = x, Length = x.Length })
            .ToLookup(x => x.Length)
            .OrderBy(x => x.Key);

        var shortests = (lookup.Count() > 0)
            ? lookup.First().Select(x => x.Value)
            : E.Empty<int[]>();

        var oStart = start / 15;
        var oEnd = end / 15;
        var offsets = E.Range(oStart, oEnd - oStart + 1).Select(x => x * 15);

        var withOffsets = from x in shortests
                          from y in offsets
                          where (start <= x.First() + y) && (x.Last() + y <= end)
                          select x.Select(z => y + z).ToArray();

        return withOffsets.ToArray();
    }
}