## Delphi For Fun Newsletter #9

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Friday, Dec 1, 2000

Well, Thanksgiving is over - I hope everyone who celebrates it had a good one.   I'll be even more thankful if we ever succeed in choosing a president, and when the stock market finishes tanking.    On the other hand, everyone here is healthy, I have a nice fat doe in the freezer and the auto-solve capability for the 15 Puzzle is working!

After a break for hunting and grandkids, here's what's been posted since last time.

November 30:  A palindromic number is one that reads the same from either end, for example 12321 or 4554.     Take any 2 digit number, reverse it and add it to the original number.  Is the result a palindrome?   If not, repeat the process until it is.   ((94+49=143, 143+341=484, a palindrome in 2 steps).  Which 2 digit number requires the most steps to reach a Palindromic Sum?

November 29: Three new clever logo contest entries from Robert in South Africa were posted today.  Check them out and vote!

I also reposted 15 Puzzle #2 with a minor correction to the hashing code.   For  large solutions, when the hash tables fill up they are automatically expanded - in theory.  Now it works in practice too.

November 28:  Whew!  15 Puzzle #2 is available.  That was almost too much fun.  It solves most puzzles in some fashion, although optimal solutions turn out to be very hard to calculate for large (5X5) boards.  It was discouraging to find a paper published in the Journal of Artificial Intelligence describing the first 10 random optimal solutions ever found for the 5X5 board .  Run times were from hours to months and board configurations evaluated ranged from 8 billion to 8 trillion per case!   I can guarantee that any  5X5's you solve with this program will not be optimal.  But probably still better than you can do by hand.   In any event, after 50-100 hours of work, I'm ready to for a new (and simpler) problem.    By the way, it's not very well documented but if you try this program, increasing the Weight value to 50 or 100 is the key to getting some solution for large problems.

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Gary
http://www.delphiforfun.org
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"If one is master of one thing and understands one thing well, one has at the same time gained insight into, and understanding of, many things." -- Vincent Van Gogh