using System;

public class Program

{

    public static int n,m;

    public static int numIslands(char[][] grid)

    {

        n = grid.Length;

        if (n==0) return 0;

        m = grid[0].Length;

        int count = 0;

        for(var i=0;i<n;i++)

        {

            for(var j=0;j<m;j++)

            {

                if(grid[i][j] == '1')

                {

                    for(var k=0;k<n;k++)

                    {           

                        Console.WriteLine(string.Join(".", grid[k]));

                    }

                    explore(grid, i, j);

                    Console.WriteLine("Count: " + count);

                    count++;

                }

            }

        }

        return count;

    }

    public static void explore(char[][] grid, int i, int j)

    {

        Console.WriteLine("i: " + i + " , j: " + j);

        if(i<0 || j<0 || i>=n || j>=m || grid[i][j] != '1')

            return;

        grid[i][j] = '0';

        explore(grid, i-1, j);

        explore(grid, i+1, j);

        explore(grid, i, j-1);

        explore(grid, i, j+1);

    }   

    public static void Main()

    {

        char[][] arr = new char[4][]

        {

            new char[5] {'1','1','0','0','0'}, 

            new char[5] {'1','1','0','0','0'},

            new char[5] {'0','0','1','0','0'},

            new char[5] {'0','0','0','1','1'}

        };

        Console.WriteLine(numIslands(arr));

    }

}

​

​

​