zby,
You can use only the information outlined by the riddle itself:

• Given: 12 balls identical in appearance
• Given: 11 balls are identical in weight, 1 is not
• Given: A balance scale with 2 sides
• Given: The use of the balance 3 times
• Goal: A set of groupings and weighings that when followed will determine which ball is odd and how it is odd.

I really don't know how else to say it. You are designing a program to solve a problem that is presumably too difficult to solve otherwise. You feed it rules to follow and a desired outcome and it churns away until it has satisified the goal.

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