I had this interesting challenge from my colleague. He asked me to draw diamond recursively (not really draw, but plot using command line program :D). I managed to draw the 3×3 diamond, but I didn’t satisfied with my program. So I put more thought on it, and make it more interesting by allow us to define the width and the height of the diamond.

namespace ConsolePrograms
{
    class DrawDiamond
    {
        static void Main(string[] args)
        {            
            Console.WriteLine("1 Diamond, Width=7, Height=5");
            SetupDiamond(1, 7, 5);
            Console.WriteLine("4 Diamond, Width=3, Height=5");
            SetupDiamond(4, 3, 5);
            Console.WriteLine("9 Diamond, Width=3, Height=3");
            SetupDiamond(9, 3, 3);
            Console.WriteLine("16 Diamond, Width=7, Height=7");
            SetupDiamond(16, 7, 7);
        }

        static void SetupDiamond(int NumberOfDiamonds, int Width, int Height)
        {
            //NumberOfDiamonds must be a Perfect Square
            if (((int)Math.Pow(Math.Sqrt(NumberOfDiamonds),2.0)) != NumberOfDiamonds)
                return;

            //Width and Height must be an odd number bigger than 1
            if (Width % 2 != 1 || Height % 2 != 1)
                return;

            int actualWidth = (int)Math.Sqrt(NumberOfDiamonds) * Width 
                - ((int)Math.Sqrt(NumberOfDiamonds)-1) ;

            int actualHeight = (int)Math.Sqrt(NumberOfDiamonds) * Height 
                - ((int)Math.Sqrt(NumberOfDiamonds)-1);

            int midWidth = (actualWidth - (actualWidth % 2)) / 2;
            int midHeight = (actualHeight - (actualHeight % 2)) / 2;

            Char[][] arCharacters = new Char[actualWidth ][];
            for (int i = 0; i < actualWidth; i++)
                arCharacters[i] = new Char[actualHeight];

            for (int i = 0; i < actualWidth; i++)
                for (int j = 0; j < actualHeight; j++)
                    arCharacters[i][j] = '.';
           
            DrawDiamond(midWidth, 0, (Width-1)/2, 
                (Height-1)/2, midWidth, midHeight, 
                actualWidth, actualHeight, 
                ref arCharacters);

            for (int i = 0; i < actualHeight ; i++)
            {
                for (int j = 0; j < actualWidth; j++)
                    Console.Write(arCharacters[j][i]);
                Console.WriteLine();
            }
        }

        public static void DrawDiamond(int x, int y, int Width, 
            int Height, int midWidth, int midHeight, 
            int actualWidth, int actualHeight, 
            ref Char[][] arCharacters)
        {             
            if (x < 0 || x >= actualWidth)
                return;
            
            if (y >= actualHeight)
                return;

            arCharacters[x][y] = '*';

            if (x < midWidth && y < midHeight)
            {
                DrawDiamond(x - Width, y + Height, Width, 
                    Height, midWidth, midHeight, 
                    actualWidth, actualHeight, 
                    ref arCharacters);
            }
            else if (x > midWidth && y < midHeight)
            {
                DrawDiamond(x + Width, y + Height, Width, 
                    Height, midWidth, midHeight, 
                    actualWidth, actualHeight, 
                    ref arCharacters);
            }
            else if (x < midWidth && y > midHeight)
            {
                DrawDiamond(x + Width, y + Height, Width, 
                    Height, midWidth, midHeight, 
                    actualWidth, actualHeight, 
                    ref arCharacters);
            }
            else if (x > midWidth && y > midHeight)
            {
                DrawDiamond(x - Width, y + Height, Width, 
                    Height, midWidth, midHeight, 
                    actualWidth, actualHeight, 
                    ref arCharacters);
            }
            else if (x == midWidth)
            {
                DrawDiamond(x - Width, y + Height, Width, 
                    Height, midWidth, midHeight, 
                    actualWidth, actualHeight, 
                    ref arCharacters);
                DrawDiamond(x + Width, y + Height, Width,
                    Height, midWidth, midHeight, 
                    actualWidth, actualHeight, 
                    ref arCharacters);
                DrawDiamond(x, y + (Height*2), Width, 
                    Height, midWidth, midHeight, 
                    actualWidth, actualHeight, 
                    ref arCharacters);
            }
            else if (x < midWidth && y == midHeight)
            {
                DrawDiamond(x + Width, y + Height, Width, 
                    Height, midWidth, midHeight, 
                    actualWidth, actualHeight, 
                    ref arCharacters);
            }
            else if (x > midWidth && y == midHeight)
                DrawDiamond(x - Width, y + Height, Width, 
                    Height, midWidth, midHeight, 
                    actualWidth, actualHeight, 
                    ref arCharacters);
            return;
        }
    }
}