Ex 4

using System;
using System.Collections.Generic;

namespace SandBox
{
    public class Program
    {
        static void Main(string[] args)
        {
            Queue<Tuple<int, int>> q = new Queue<Tuple<int, int>>();
            string d = Console.ReadLine();
            int n = Convert.ToInt32(d.Split(' ')[0]);
            int m = Convert.ToInt32(d.Split(' ')[1]);
            List<List<char>> lab = new List<List<char>>(n);

            for (int i = 0; i < n; i++)
            {
                lab.Add(new List<char>(m));
                for (int j = 0; j < m; j++)
                {
                    lab[i].Add('_');
                }
            }

            for (int i = 0; i < n; i++)
            {
                string col = Console.ReadLine();
                for (int j = 0; j < m; j++)
                {
                    lab[i][j] = col[j];
                }
            }

            for (int i = 0; i < n; i++)
            {
                for (int j = 0; j < m; j++)
                {
                    if (lab[i][j] == 'S')
                    {
                        q.Enqueue(new Tuple<int, int>(i,j));
                    }
                }
            }

            while (q.Count > 0)
            {
                Tuple<int, int> tmp = q.Dequeue();

                if (tmp.Item1 - 1 >= 0 && lab[tmp.Item1 - 1][tmp.Item2] == '.')
                {
                    q.Enqueue(new Tuple<int, int>(tmp.Item1 - 1, tmp.Item2));
                    lab[tmp.Item1 - 1][tmp.Item2] = 'U';
                }
                if (tmp.Item1 + 1 < n && lab[tmp.Item1 + 1][tmp.Item2] == '.')
                {
                    q.Enqueue(new Tuple<int, int>(tmp.Item1 + 1, tmp.Item2));
                    lab[tmp.Item1 + 1][tmp.Item2] = 'D';
                }
                if (tmp.Item2 - 1 >= 0 && lab[tmp.Item1][tmp.Item2 - 1] == '.')
                {
                    q.Enqueue(new Tuple<int, int>(tmp.Item1, tmp.Item2 - 1));
                    lab[tmp.Item1][tmp.Item2 - 1] = 'L';
                }
                if (tmp.Item2 + 1 >= 0 && lab[tmp.Item1][tmp.Item2 + 1] == '.')
                {
                    q.Enqueue(new Tuple<int, int>(tmp.Item1, tmp.Item2 + 1));
                    lab[tmp.Item1][tmp.Item2 + 1] = 'R';
                }
            }

            foreach (var s in lab)
            {
                foreach (var s1 in s)
                {
                    Console.Write(s1);
                }
                Console.WriteLine();
            }
        }
    }
}