using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        int[,] map = new int[4,5] {   { 0, 0, 1, 1, 0 },

                                          { 1, 0, 1, 1, 0 },

                                          { 0, 1, 0, 0, 0 },

                                          { 0, 0, 0, 0, 1 } };

        Console.WriteLine(BFSgetBiggestRegion(map));

    }

    public static int BFSgetBiggestRegion(int[,] matrix)

        {

            int maxRegion = 0;

​

            for (int row = 0; row < matrix.GetLength(0); row++)

            {

                for (int column = 0; column < matrix.GetLength(1); column++)

                {

                    if (matrix[row, column] == 1)

                    {

                        int size = BFSgetRegionSize(matrix, row, column);

                        maxRegion = Math.Max(size, maxRegion);

                    }

                }

            }

​

            return maxRegion;

        }

​

        public static Queue<Tuple<int, int>> coordinates = new Queue<Tuple<int, int>>();

        public static HashSet<Tuple<int, int>> visited = new HashSet<Tuple<int, int>>();

​

        private static int BFSgetRegionSize(int[,] matrix, int row, int column)

        {

            if (row < 0 || column < 0 || row >= matrix.GetLength(0) || column >= matrix.GetLength(1))

            {

                return 0;

            }

            if (matrix[row, column] == 0 || visited.Contains(new Tuple<int, int>(row, column)))

            {

                return 0;

            }

​

            visited.Add(new Tuple<int, int>(row, column));

            int size = 1;

            for (int r = row - 1; r <= row + 1; r++)

            {

                for (int c = column - 1; c <= column + 1; c++)

                {

                    if ((r != row || c != column) && !visited.Contains(new Tuple<int, int>(r, c)))

                    {

                        coordinates.Enqueue(new Tuple<int, int>(r, c));

                    }

                }

            }

​

            while (coordinates.Any())

            {

                var point = coordinates.Dequeue();

                size += BFSgetRegionSize(matrix, point.Item1, point.Item2);

​

            }

            return size;

        }

}