public class Htree {

    // plot an H, centered on (x, y) of the given side length
    public static void drawH(double x, double y, double size) {
        double xl = x - size/2, xr = x + size/2;
        double yl = y - size/2, yu = y + size/2;
        StdDraw.line(xl,  y, xr,  y);
        StdDraw.line(xl, yl, xl, yu);
        StdDraw.line(xr, yl, xr, yu);
    }

    // plot an order n H-tree, centered on (x, y) of the given side length
    public static void draw(int n, double x, double y, double size) {
        if (n == 0) return;
        drawH(x, y, size);
        double xl = x - size/2, xr = x + size/2;
        double yl = y - size/2, yu = y + size/2;
        draw(n-1, xl, yl, size/2);
        draw(n-1, xl, yu, size/2);
        draw(n-1, xr, yl, size/2);
        draw(n-1, xr, yu, size/2);
    }

    // read in a command line parameter N and plot an order N H-tree
    public static void main(String[] args) {
        int N = 5;//Integer.parseInt(args[0]);
        StdDraw.setPenRadius(0.005);
        draw(N, .5, .5, .5);
    }
}