Quiz #109 even leaves it up to the implementer whether to go clockwise
or counter-clockwise.  So it's designed to have some flexibility in it.
 In fact, it's typical of the Ruby Quiz to define a core problem and
leave many of the details up to the individual implementers.  And given
that the Quiz is designed to enhance understanding and appreciation of
Ruby (and not to be an exam or contest) that seems reasonable.

However, addressing your narrower point, the sample output provided in
the quiz statement does use an even number (8) to define the size.  And
as you can see from the sample output, the 0 is located just to the
right and just below the exact center.  So you could reasonably use
that to nail down that detail.

Eric

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Josef 'Jupp' Schugt wrote:
> * Ruby Quiz, 01/12/2007 03:29 PM:
> > The number zero represents the center of the spiral
>
> Let me suggest that you address the issue of the centre being
> ill-defined under the condition that the number of columns/rows is
> even. Given that altogether four positions meet the condition leaving
> this question open will result in a multitude of different outputs
> that are solutions of the task. In my opinion a programming quiz
> should use a well-posed problem so that the different programs can be
> compared directly. Especially if the problem can be solved by
> constructing a clever mathematical formula which my intuition suggest
> to be the case with the number spiral problem (I did not yet try to
> verify this).
> 
> Jupp