HackerRank - Connected Cell In a Grid - use queue, two dimension array, and also, not use recursive call, using loops instead.

ConnectedCellInaGrid2.cs

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

static class Program
{
    static void Main(string[] args)
    {
        int m = Convert.ToInt32(Console.ReadLine());
        int n = Convert.ToInt32(Console.ReadLine());

        int[,] matrix = new int[m, n];
        for (int r = 0; r < m; r++)
        {
            string line = Console.ReadLine();
            int c = 0;
            foreach (char ic in line)
            {
                if (ic == '0' || ic == '1')
                {
                    int v = (int)(ic - '0');
                    matrix[r, c++] = v;
                }
            }
        }

        Console.WriteLine(MaxRegion(m, n, matrix));
    }

    static int MaxRegion(int m,
                         int n,
                         int[,] matrix)
    {
        int maxRegion = Int32.MinValue;

        for (int r = 0; r < m; r++)
        {
            for (int c = 0; c < n; c++)
            {
                int region = 0;
                if (matrix[r, c] == 1)
                {
                    Queue queue = new Queue();
                    int key = r * n + c;
                    matrix[r, c] = 2;
                    queue.Enqueue(key);
                    region = 0;
                    while (queue.Count > 0)
                    {
                        key = (int)queue.Dequeue();
                        int row = key / n;
                        int col = key % n;
                        region++;
                        for (int dr = -1; dr <= 1; dr++)
                        {
                            for (int dc = -1; dc <= 1; dc++)
                            {
                                int nrow = row + dr;
                                int ncol = col + dc;
                                if (nrow >= 0 &&
                                    nrow < m &&
                                    ncol >= 0 &&
                                    ncol < n &&
                                    matrix[nrow, ncol] == 1)
                                {
                                    key = nrow * n + ncol;
                                    matrix[nrow, ncol] = 2;
                                    queue.Enqueue(key);
                                }
                            }
                        }
                    }
                }

                if (region > maxRegion)
                {
                    maxRegion = region;
                }
            }
        }

        return maxRegion;
    }
}