Nit$ hajó$kapitány vizei

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Diagnostics;
using System.IO;

namespace SearchForIsland
{
    class Position
    {
        public int x { get; private set; }
        public int y { get; private set; }

        public Position(int a, int b)
        {
            x = a;
            y = b;
        }
    }
    class Water
    {
        public Position tl { get; private set; }
        public Position br { get; private set; }

        public int GetSize()
        {
            return (br.x - tl.x) * (br.y - tl.y);
        }

        public Water(Position a, Position b)
        {
            tl = a;
            br = b;
        }
    }

    class Program
    {
        static void ReadFile(byte filenum)
        {
            string[] lines = File.ReadAllLines($"fel{filenum}.txt");
            int linelength = lines.Length;
            int columnlength = lines[0].Length;
            source = new char[linelength + 1, columnlength + 1];
            for (int i = 1; i <= linelength; i++)
            {
                for (int j = 1; j <= columnlength; j++)
                {
                    source[i, j] = lines[i - 1][j - 1];
                }
            }
        }

        static void FillHelper(string fn)
        {
            StreamWriter sw = new StreamWriter(fn);
            helper = new int[source.GetLength(0), source.GetLength(1)];
            for (int i = 1; i < source.GetLength(0); i++)
            {
                for (int j = 1; j < source.GetLength(1); j++)
                {
                    helper[i, j] = helper[i - 1, j] + helper[i, j - 1] - helper[i - 1, j - 1] + (source[i, j] == '#' ? 0 : 1);
                    sw.Write($"{helper[i, j]}\t");
                }
                sw.WriteLine();
            }
            sw.Close();
        }

        static int NumOfIslands(int r1, int c1, int r2, int c2)
        {
            return helper[r2, c2] + helper[r1 - 1, c1 - 1] - helper[r1 - 1, c2] - helper[r2, c1 - 1];
        }

        static Water GetGreatest()
        {
            Water max = new Water(new Position(0, 0), new Position(0, 0));
            for (int r1 = 1; r1 < helper.GetLength(0); r1++)
            {
                for (int c1 = 1; c1 < helper.GetLength(1); c1++)
                {
                    for (int r2 = r1; r2 < helper.GetLength(0); r2++)
                    {
                        for (int c2 = c1; c2 < helper.GetLength(1); c2++)
                        {
                            if (NumOfIslands(r1, c1, r2, c2) == 0)
                            {
                                Water current = new Water(new Position(r1, c1), new Position(r2, c2));
                                if (max.GetSize() < current.GetSize())
                                {
                                    max = current;
                                }
                            }
                            else break;
                        }
                    }
                }
            }
            return max;
        }

        static void SetGreatest()
        {
            for (int i = max.tl.x; i <= max.br.x; i++)
            {
                for (int j = max.tl.y; j <= max.br.y; j++)
                {
                    source[i, j] = 'M';
                }
            }
        }

        static void WriteMatrix()
        {
            for (int i = 0; i < source.GetLength(0); i++)
            {
                for (int j = 0; j < source.GetLength(1); j++)
                {
                    Console.Write($"{source[i, j]}");
                }
                Console.WriteLine();
            }
        }

        static void WriteEx(byte num, Water greatest, int ms)
        {
            if (greatest.GetSize() == 0)
                Console.WriteLine($"{num}.: Nincs víz!");
            else
                Console.WriteLine($"{num}.: Bal felső: {greatest.tl.x}x{greatest.tl.y}; Jobb alsó: {greatest.br.x}x{greatest.br.y}; Méret: {greatest.GetSize()}; T = {ms}ms");
        }

        static char[,] source;
        static int[,] helper;
        static Water max;

        static void DoEx(byte num, int ms)
        {
            source = null;
            helper = null;
            max = null;
            ReadFile(num);
            FillHelper($"Szigetek{num}.txt");
            max = GetGreatest();
            WriteEx(num, max, ms);
        }

        static void Main(string[] args)
        {
            /*Console.WriteLine("Feladatszám: ");
            byte n = byte.Parse(Console.ReadLine());
            ReadFile(n);
            FillHelper("Szigetek1.txt");
            max = GetGreatest();
            SetGreatest();
            WriteMatrix();*/
            Stopwatch st = new Stopwatch();
            for (int i = 1; i < 10; i++)
            {
                st.Start();
                DoEx((byte)i, (int)st.ElapsedMilliseconds);
                st.Stop();
            }
            Console.ReadLine();
        }
    }
}