SpiralMatrix

using System;

class SpiralMatrix
{
    static void Main()
    {
       Console.Write("n=");
        int n = int.Parse(Console.ReadLine());
        int i = 0;
        int j = 0;
        char dir = 'r';
        if (n >= 1 && n <= 100)
        {
            int[,] mass = new int[n,n];
            for (int st = 1; st <= n*n; st++)
            {
                if (dir == 'r' && (j > n - 1 || mass[i, j] != 0))
                {
                    dir = 'd';
                    j--;
                    i++;
                }
                if (dir == 'd' && (i > n - 1 || mass[i, j] != 0))
                {
                    dir = 'l';
                    i--;
                    j--;
                }
                if (dir == 'l' && (j < 0 || mass[i, j] != 0))
                {
                    dir = 'u';
                    j++;
                    i--;
                }
                if (dir == 'u' && (i < 0 || mass[i, j] != 0))
                {
                    dir = 'r';
                    i++;
                    j++;
                }
                mass[i, j] = st;

                switch (dir)
                {
                    case 'u': i--;
                        break;
                    case 'd': i++;
                        break;
                    case 'l': j--;
                        break;
                    case 'r': j++;
                        break;
                }

            }
            for (int r = 0; r < n; r++)
            {
                for (int c = 0; c < n; c++)
                {
                    Console.Write("{0,2}", mass[r, c]);
                }
                Console.WriteLine();
            }
        }
        else
        {
            Console.WriteLine("Error. Bad input!");
        }
    }
}