unforum

[rhysara]

Ok, I admit it. This card drives me nuts. The reason no doubt is that for the first week or so I was working under the assumption that the only thing that mattered was that the 14 and 15 be in the correct locations and that the blank be in the top left corner.

Almost half of my incorrect solves stem from this misconception. (And let me assure you that I can solve the problem that way in remarkably few moves).

Needless to say by the time I finally clued in, I was so annoyed about the whole thing that I wanted nothing to do with it. In an attempt to make me feel better about the whole thing (and get me to solve the stupid thing), one of my close friends made me a spiffy little web based program to solve (and better yet record and display) my solutions to the problem.

Since I imagine I'm not the only one who would like to solve this card and be done with it. I thought I would post a link to the webpage/program he wrote for me. Hope this helps!

Again, this is all web based, no need to download anything!

http://outpost.lothar.com/173.rpy

Instructions: Everything is done through the URL, so to "undo" you just hit the browser's Back button. If you're part-way through a solution and want to remember where you were so you can try something else, just bookmark it.

It even has a high-score feature (although its only tracking a personal
best, there isn't anything to compare your shortest path against other
people's).

[e_nygma]

While bouncing around trying to find a suggested way to solve this puzzle (and then later on throwing up my hands and using what cronogenesis did (thanks!)), I came across the following:

http://www.elversonpuzzle.com/The-15-Puzzle-Book.html
http://www.chaichart.com/phpwebsite/topics.php?op=viewtopic&topic=5

According to Jerry Slocum, a "world-renown (sic) mechanical puzzle collector, historian, and writer" (quote from second link), Sam Loyd had nothing to do with inventing the puzzle or publicizing it.

More ironically, he told of his research (before the book was published) during his acceptance speech while accepting the Association of Game & Puzzle Collectors (AGPC) award for "an individual who, as an entrepreneur, has been responsible for the promotion of mechanical puzzles through their design, development, or manufacture."

[almagest]

"how the hoax lasted more than a century"

I find that unbelievable, since it is trivial to prove that it is impossible (any maths freshman should be able to do it - it is just an easy parity argument).

But maybe there are none so deaf as those that do not want to hear!

[almagest]

Coming back to the puzzle, does anyone have any ideas on proving 44 optimal?

I can see that one can probably write a program that searches some huge number of possibilities and finds a shortest solution that way.

But that sounds like a lot of hard work, and I would be sceptical of anyone else's program (without spending a lot of time looking at the source code).

Each move changes the position of just one digit by one orthogonal position. Counting up we need at least 24 such changes. One can up that a bit because you have to move 14 (for example) to get 15 into the right position. But I cannot get anywhere near 44.

Has anyone any better ideas?

[mcdon2401]

[marion]

thankee

[clahey]

IDA*