Question

Note 1: I already have the brute force, verbose, loopy messy code in place.
Note 2: Looking for more elegant ways of establishing this – “lesser” number of lines and clever logic.
Note 3: Not homework, I am a hobbyist trying to improve.

Function to be coded:

printNumericPyramid(int depth, String alignment, String orientation);

depth: +ve integer up to 4
alignment: one of “left”/”right”
orientation: one of “upright”/”inverted”

0 will always be at the apex, whether upright or inverted
0259/9520 will always be the height of the pyramid.

---

Samples calls and expected outputs:

printNumericPyramid(4, "left", "inverted");

9876
543.
21..
0...

printNumericPyramid(4, "right", "upright");

...0
..12
.345
6789

printNumericPyramid(4, "right", "inverted");

6789
.345
..12
...0


printNumericPyramid(4, "left", "upright");

0...
21..
543.
9876

It would be great if “lesser” number of lines could be the focus of the proposed solution. Not by removing all linebreaks:), but by minimization of code (even if it hurts readibility).

Answer 1

(First note that your method definition is error-prone: if an argument can only take two values you can use a boolean instead of a String. If you mispell “left” or “right” or “inverted” or “upright”, your method will work yet produce the wrong result)

If you want to focus on a low number of lines then you should not repeat yourself and you can make use of the ternary operator and of the available Java APIs.

You could write a very short solution based on very “smart” and totally unreadable code inside the following kind of loop:

   public void printNumericPyramid( final int depth, final String alignment, final String orientation ) {
        for (int i = 0; i < depth; i++) {
            for (int j = 0; j < depth; j++) {
                System.out.print ( ... ) // insert some smart hackery in here computing if we should print 0-9 or '.'
            }
            System.out.println();
        }
    }

However this may not end up being that easy to read and it’s going to be easy to get the logic wrong.

So I wrote another solution:

• at each character you either print the next value (from 0 to 9) or you print a dot ‘.’.

• when a line is “done”, I either add that line or that line reversed, depending on the value of the alignment parameter.

• if the inversed representation is asked, you can simply reverse the collection

  public void printNumericPyramid( final int depth, final String alignment, final String orientation ) {
      final List<String> l1 = new ArrayList<String>();
      for (int i = 0, c = 0; i < depth; i++) {
          final StringBuilder sb = new StringBuilder();
          for (int j = 0; j < depth; j++) {
              sb.append( j >= depth - (i + 1) ? c++ : "." );
          }
          l1.add("left".equals(alignment) ? sb.reverse().toString() : sb.toString());
      }
      if ( "inverted".equals(orientation) ) Collections.reverse(l1);
  
      for ( final String s : l1 ) {
          System.out.println( s );
      }
  }