20170427, 23:01  #1 
"Robert Gerbicz"
Oct 2005
Hungary
17·97 Posts 
May 2017
There is a new Ibm puzzle:
https://www.research.ibm.com/haifa/p...s/May2017.html 
20170501, 16:02  #2 
Just call me Henry
"David"
Sep 2007
Liverpool (GMT/BST)
2^{2}×1,553 Posts 
Brute force seems to run out of steam at around n=15. Not sure what to do next.

20170501, 16:17  #3 
"Ed Hall"
Dec 2009
Adirondack Mtns
2^{2}·1,439 Posts 
I wrote program that gives me thousands of valid answers, but how to translate it into a formula escapes me...
Edit: I wrote the program with embedded loops, hoping that once I found a valid string, I could create a formula, but alas, I can't get there from there... Last fiddled with by EdH on 20170501 at 16:20 
20170501, 16:38  #4 
Just call me Henry
"David"
Sep 2007
Liverpool (GMT/BST)
2^{2}·1,553 Posts 
You are brave doing that many embedded loops. I chose recursion.

20170501, 16:41  #5 
"Rashid Naimi"
Oct 2015
Remote to Here/There
41·59 Posts 
Without the 53 character limit, it would be trivial to come up with a solution, just line them up.
With the restriction however the brute force will require astronomical execution times to come up with a solution if such solutions are rare. Perhaps someone can do the number of atoms comparison here. I think running the brute force intelligently is the best approach. Running the brute force from large strings to lower should yield results faster (there are other similar improvement possible). Another improvement would be stop executing inner loops as soon as a conflict is found. But with 26 nested loops, it is a pain to code. I have tried but can't afford to invest enough time to optimize the code. 
20170501, 16:41  #6 
"Robert Gerbicz"
Oct 2005
Hungary
17×97 Posts 
What formula? You need to find a valid string with no more than 53 characters... (it is likely it'll be a meaningless word). And send it with description how you found it (optionally with a code).

20170501, 16:56  #7 
"Rashid Naimi"
Oct 2015
Remote to Here/There
100101110011_{2} Posts 
If the solutions are abundant enough, then a random search might find a solution faster than an organized brute force.

20170501, 18:11  #8  
"Ed Hall"
Dec 2009
Adirondack Mtns
2^{2}×1,439 Posts 
Quote:
Can I post one of the stings here for review or would that share too much info for the challenge? 

20170501, 18:31  #9  
"Robert Gerbicz"
Oct 2005
Hungary
17×97 Posts 
Quote:
Here do not post full/partial solutions. You can do that only after the contest, when the official solution appears. 

20170501, 18:38  #10  
"Ed Hall"
Dec 2009
Adirondack Mtns
2^{2}·1,439 Posts 
Quote:


20170501, 18:48  #11 
"Robert Gerbicz"
Oct 2005
Hungary
17·97 Posts 
OK, it is not a very complicated process. Furthermore what I generally follow is that if you use a special program (say Maple/Mathematica/Matlab) or even a free program then submit also the screen output. You don't need it for c/c++/PariGp code because it is so general, he can even run it easily if he wants it.
Last fiddled with by R. Gerbicz on 20170501 at 18:48 
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