Task
Produce an ASCII representation of a Sierpinski triangle of order   N.



Example
The Sierpinski triangle of order   4   should look like this:

                       *
                      * *
                     *   *
                    * * * *
                   *       *
                  * *     * *
                 *   *   *   *
                * * * * * * * *
               *               *
              * *             * *
             *   *           *   *
            * * * *         * * * *
           *       *       *       *
          * *     * *     * *     * *
         *   *   *   *   *   *   *   *
        * * * * * * * * * * * * * * * *



Related tasks
 Sierpinski triangle/Graphical for graphics images of this pattern. 
 Sierpinski carpet


 
 
public class SierpinskiTriangle {
 
    public static void main(String[] args) {
        System.out.println(getSierpinskiTriangle(4));
    }
 
    private static final String getSierpinskiTriangle(int n) {
        if ( n == 0 ) {
            return "*";
        }
 
        String s = getSierpinskiTriangle(n-1);
        String [] split = s.split("\n");
        int length = split.length;
 
        //  Top triangle
        StringBuilder sb = new StringBuilder();
        String top = buildSpace((int)Math.pow(2, n-1));
        for ( int i = 0 ; i < length ;i++ ) {
            sb.append(top);
            sb.append(split[i]);
            sb.append("\n");
        }
 
        //  Two triangles side by side
        for ( int i = 0 ; i < length ;i++ ) {
            sb.append(split[i]);
            sb.append(buildSpace(length-i));
            sb.append(split[i]);
            sb.append("\n");
        }
        return sb.toString();
    }
 
    private static String buildSpace(int n) {
        StringBuilder sb = new StringBuilder();
        while ( n > 0 ) {
            sb.append(" ");
            n--;
        }
        return sb.toString();
    }
 
}
 