Draw H tree - recursive 30 minutes practice - C# code

DrawHTree_Recursive_30minutes.cs

using System; 

class HelloWorld
{
    static void Main()
    {
        DrawHTree(100, 100, 50, 2);
    }
  
    public static void DrawHTree(double x, double y, double length, int depth) // deppth = 1
    {
      // base case 
      if(depth == 0)        
      {
        return ; 
      }
      
      // draw One H
      var halfLength = length/ 2; 
        
      var leftX  = x - halfLength; 
      var rightX = x + halfLength; 
        
      var topY    = y + halfLength; 
      var bottomY = y - halfLength; 
        
      drawLine(leftX, y,    rightX, y);       // horizontal line
      drawLine(leftX, topY, leftX,  bottomY);  // left vertical line
      drawLine(rightX,topY, rightX, bottomY); // rigth vertical line             
      
      // draw 4 H tree in four corners 
      // four corners start from left/ top, clockwise 
      var nextLength = length/ Math.Sqrt(2); 
      var nextDepth = depth - 1; 
      
      DrawHTree(leftX,  topY,    nextLength, nextDepth); 
      DrawHTree(rightX, topY,    nextLength, nextDepth); 
      DrawHTree(rightX, bottomY, nextLength, nextDepth); 
      DrawHTree(leftX,  bottomY, nextLength, nextDepth);       
    }
  
    private static void drawLine(double x1, double y1, double x2, double y2)
    {
      
      Console.WriteLine(to3Decimal(x1) + "," + to3Decimal(y1)+" -"+to3Decimal(x2) + ","+ to3Decimal(y2)); 
    }
  
    private static double to3Decimal(double x)
    {
      return (int)(x * 1000)/ 1000.0; 
    }
}

// 1.4  3 draw line - O(1)  
// 1 + 4 + 4^2 + ... + 4^n = 4^(n + 1) - 1/ 4 - 1 = O(4^n)
// space complexity  O(n)

/*
center value (x, y), length , depth 

First H, 
(x - length/2, y + length/2)              (x +length/2, y + length/2)    
|                                            |
|
|
|


                  (x, y)
-------------------|-------------------------- (x + length/2, y )
(x - length/2, y )



|
(x- length/2, y - length/2)
*/