6.13Loops_SpiralMatrix_Reverse

using System;


class ReverseSpiralMatrix
{
    static void Main()
    {
        Console.Write("Enter a positive whole number in the range [1 ... 31], for N = ");
        string numberStr = Console.ReadLine();
        int numN = int.Parse(numberStr);

        if (numN < 1 || numN > 31)
        {
            Console.WriteLine("Error - The number is Out of Range !!!");
        }
        else
        {
            int[,] matrix = new int[numN, numN];
            int row = 0;
            int col = 0;
            string direction = "right";
            int maxValue = numN * numN;

            for (int i = maxValue; i >= 1; i--)
            {
                if (direction == "right" && (col > (numN - 1) || matrix [row, col] != 0))
                {
                    direction = "down";
                    row++;
                    col--;
                }
                if (direction == "down" && (row > (numN - 1) || matrix [row, col] != 0))
                {
                    direction = "left";
                    row--;
                    col--;
                }
                if (direction == "left" && (col < 0 || matrix [row, col] != 0))
                {
                    direction = "up";
                    row--;
                    col++;
                }
                if (direction == "up" && (row < 0 || matrix[row, col] != 0))
                {
                    direction = "right";
                    row++;
                    col++;
                }

                matrix [row, col] = i;
                if (direction == "right")
                {
                    col++;
                }
                if (direction == "down")
                {
                    row++;
                }
                if (direction == "left")
                {
                    col--;
                }
                if (direction == "up")
                {
                    row--;
                }
            }

            // Print the numbers in reverse order to spiral matrix:
            Console.WriteLine("The numbers in Reverse Spiral Matrix are:");
            for (int r = 0; r < numN; r++)
            {
                for (int c = 0; c < numN; c++)
                {
                    Console.Write("{0,4} ", matrix [r, c]);
                }
                Console.WriteLine();
            }
        }
        Console.ReadLine();
    }
}