ProjectEuler0011.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.IO;
using System.Reflection;
using EulerProject;

namespace Problem0011
{
    class Program
    {
        const int size = 20;
        const int choice = 4;
        static void Main(string[] args)
        {
            StreamReader fs = new StreamReader("data.txt", Encoding.Unicode);
            string str = fs.ReadToEnd();
            fs.Close();
            var data = str.Split('\n')
                .Select((l) => l.Split()
                    .Where((s)=>(s.Length > 0))
                    .Select((n) => (int.Parse(n)))
                    .ToArray())
                .ToArray();
            var result = new[] {
                Euler.Range(0, size - choice + 1)
                    .Select((x)=>(
                        Euler.Range(0, size)
                            .Select((y)=>(
                                Euler.Range(choice)
                                    .Select((n)=>(new{x=x+n, y=y})))))),
                Euler.Range(0, size)
                    .Select((x)=>(
                        Euler.Range(0, size - choice + 1)
                            .Select((y)=>(
                                Euler.Range(choice)
                                    .Select((n)=>(new{x=x, y=y+n})))))),
                Euler.Range(0, size - choice + 1)
                    .Select((x)=>(
                        Euler.Range(0, size - choice + 1)
                            .Select((y)=>(
                                Euler.Range(choice)
                                    .Select((n)=>(new{x=x+n, y=y+n})))))),
                Euler.Range(0, size - choice + 1)
                    .Select((x)=>(
                        Euler.Range(0, size - choice + 1)
                            .Select((y)=>(
                                Euler.Range(choice)
                                    .Select((n)=>(new{x=x+choice-n-1, y=y+n}))))))}
            .SelectMany((item)=>(item))
            .SelectMany((item)=>(item))
            .Select((n)=>(
                n.Select((a)=>(data[a.y][a.x]))
                    .Aggregate((x,y)=>(x*y))))
            .Max();


            Console.WriteLine(result);
            Console.ReadKey();
        
        }
    }
}