topic Re: Simple LabVIEW Puzzle Challenge in BreakPoint

Simple LabVIEW Puzzle Challenge

ShotSimon — Mon, 08 Sep 2008 20:45:00 GMT

I am a big fan of Games Magazine and have always enjoyed puzzles, so I decided to start a simple fun thread about puzzles. This is a perfect way to learn some tips and tricks using LabVIEW.

Since this is a programming challenge credit should be giving to speed...but I think presentation should also factor in.

The first puzzle, is a puzzle about crossing a rickety bridge in the dark. It was originally published in Games Magazine but I do not have the original reference. Four people named 1, 2, 5, and 10 have to quickly cross the bridge. They have a single flashlight and everyone needs to get safely across. 1 takes one minute, 2 takes two minutes, 5 takes five minutes, and 10 takes ten minutes. Only two people are allowed across at any one time, and you must walk the speed of the slower person.

Example:

We will have 1 and 2 go across first = 2 mins.

1 goes back = 1 min.

1 and 5 goes across = 5 mins.

for a total of 8 mins. so far.

The trick is to do this in the minimum time possible (and no you don't get to throw the flashlight).

There are solutions on the web but I would suggest if you've never seen this puzzle to avoid looking up the answer since solving it is more fun.

The trick is to be creative and have fun and I look forward to seeing your solutions.

Regards,

-SS

Re: Simple LabVIEW Puzzle Challenge

RavensFan — Mon, 08 Sep 2008 21:45:11 GMT

It sounds like an interesting idea to try to solve these kinds of puzzles using LabVIEW. But I would recommend finding the original writeup on this particular puzzle. It sounds like this puzzle has a pretty easy solution that the 1 minute guy be the one who leads the others across and brings the flashlight back. There must be some other catch to this described in the puzzle writeup that makes this more of a puzzle.

Re: Simple LabVIEW Puzzle Challenge

ShotSimon — Mon, 08 Sep 2008 21:51:48 GMT

ShotSimon wrote:
Only two people are allowed across at any one time, and you must walk the speed of the slower person.

Ravens Fan,

Does that line clear things up a bit I did try to find the original source but no luck, I'll keep looking.

I was afraid I would confuse people. Let me know if it's clear now?

-SS

Re: Simple LabVIEW Puzzle Challenge

smercurio_fc — Mon, 08 Sep 2008 22:43:43 GMT

Not really. Ravens Fan is right. In your description you stated that only two people are allowed to cross, but in your example you indicate that 1 goes back alone. This would seem to contradict the rules of crossing. There must be something missing from the puzzle, otherwise there's no reason not to have 1 take the trip back each time, and there would be only one (no pun intended) solution to the "puzzle".

Re: Simple LabVIEW Puzzle Challenge

RavensFan — Tue, 09 Sep 2008 01:24:51 GMT

Okay, it is not as trivial as I thought. (I was at work, and work was distracting me ) I thought the easy solution was 1&8 across (8) 1 back (1) 1&4 across (4) 1 back (1) 1 and 2 across (2), total 16 minutes.

Then I realized the trick was to try to minimize the times of the going over even if it costs you some time on the going back. And the only way to do that was to merge the 4 guy with the 8 guy, but never let one of them walk back because you've already had 1 & 2 go across ahead of them.

1 & 2 across (2) 1 back (1) 4 & 8 across (8) 2 back (2) 1&2 across (2), total 15 minutes.

Is there any better solution?

Of course this could be done in LabVIEW or any programming language. Probably generating a table that sets up all the permutations of over and back for the different people, doing the calculations, then sorting the list to find the one that has the lowest total.

The other possibility is that it is an interactive game where a user clicks on each person, the program determines whether it is a valid move, logs it and totals the time. Then it could keep track of the lowest time to date and the corresponding moves and allows the player to try again.

I had forgotten about Games magazine. My sister used to get it back when we were kids. I would read it and do the puzzles after she was done with it. They had a lot of really good logic puzzles that sometimes seemed downright impossible. Is the magazine still around?

Message Edited by Ravens Fan on 09-08-2008 09:24 PM

Re: Simple LabVIEW Puzzle Challenge

ShotSimon — Tue, 09 Sep 2008 14:51:16 GMT

smercurio_fc wrote:
"In your description you stated that only two people are allowed to cross, but in your example you indicate that 1 goes back alone. This would seem to contradict the rules of crossing."
Ravens Fan wrote:
"1&8 across (8) 1 back (1) 1&4 across (4) 1 back (1) 1 and 2 across (2), total 16 minutes."

Sorry for the late reply, Enthusiast's are a tough crowd

OK some clarification is needed. The idea is that the bridge can only handle at most two people. One person can certainly cross alone and needs to in order to bring the flashlight safely back to the others. You need the flashlight for safety as it is a dark rickety bridge

The actual description of this puzzle was something like two sentences so you have to make assumptions about not cheating, etc.

Raven's Fan is on the right track but were he came up with 4 and 8 I'll never know. It's interesting to note with software it could be any four positive integers. It would be interesting to see which give the best result for example. For now lets stick with 1, 2, 5, and 10.

Also if you get a solution I was hoping people would post in LabVIEW.

I can tell you the answer which was also in the original problem and it is "17". There is no doubt most people can solve this on paper in a few minutes but I think you will enjoy the solution. In a way it is not common sense. For example 1 is not the person who is used the most, as most people would think.

Enjoy, I will post a solution once I feel people have had an adequate go at it

-SS

Message Edited by ShotSimon on 09-09-2008 09:51 AM

Re: Simple LabVIEW Puzzle Challenge

tst — Tue, 09 Sep 2008 14:56:34 GMT

Ravens Fan already provided the solution. Adapting his numbers to 5 and 10 results in 17 minutes.

Re: Simple LabVIEW Puzzle Challenge

RavensFan — Tue, 09 Sep 2008 15:30:56 GMT

I have no idea where I got 1, 2, 4, and 8 from either. I think went back to read the original message I saw the 8 total minutes in the example and must have run with that.

I must have started thinking in binary numbers, 1, 2, 4, 8

My original guess should have been

1&10 across (10) 1 back (1) 1&5 across (5) 1 back (1) 1 and 2 across (2), total 19 minutes.

and the correct guess as tst said:

1 & 2 across (2) 1 back (1) 5 & 10 across (10) 2 back (2) 1&2 across (2), total 17 minutes.

The other correct answer would be 2 coming back first and 1 coming back 2nd which would be the same total time.

Message Edited by Ravens Fan on 09-09-2008 11:30 AM

Re: Simple LabVIEW Puzzle Challenge

ShotSimon — Tue, 09 Sep 2008 15:46:03 GMT

You guys are cracking me up

I'm looking for a LabVIEW solution for people to show off there creativity and coding skills, not for someone to post the solution.

Part of the fun with puzzles is to see how others solve it, even if you already know the solution.

-SS

Re: Simple LabVIEW Puzzle Challenge

RavensFan — Tue, 09 Sep 2008 15:57:06 GMT

I did post a couple of ideas in reply 5. But I don't feel like putting in all the effort to actually code something up. Too many projects at work and at home I should be doing.

Which were you thinking of as the challenge, LV program to solve and finding the solution? Or a LV program as a game to help a person to discover the solution.?

Re: Simple LabVIEW Puzzle Challenge

ShotSimon — Tue, 09 Sep 2008 16:01:08 GMT

Ravens Fan wrote:
Which were you thinking of as the challenge, LV program to solve and finding the solution? Or a LV program as a game to help a person to discover the solution.?

Either would be acceptable, but the game sounds like it would take longer. -SS

Re: Simple LabVIEW Puzzle Challenge

Darren — Tue, 09 Sep 2008 17:19:25 GMT

Ok, I'll go first. Here's a brute force approach that discovers the optimal time very quickly. Theoretically this approach could take an extremely long time if the random pulls are infinitely unlucky. I'm guessing some math whiz could come up with a better way to pre-calculate all the possible combinations and just run through those.

Here's a screenshot of the diagram, and the VI (saved in LabVIEW 7.0) is attached below.

-D

P.S. - GAMES magazine is awesome! My favorite puzzles are Cryptic Crosswords and Cartoon Rebuses.

Message Edited by Darren on 09-09-2008 12:19 PM

Re: Simple LabVIEW Puzzle Challenge

ShotSimon — Tue, 09 Sep 2008 17:34:45 GMT

Darren,

Excellent! I love the icon -SS

Re: Simple LabVIEW Puzzle Challenge

ShotSimon — Tue, 09 Sep 2008 21:30:32 GMT

Darren,

After further review I realize your solution doesn't actually provide or show the order of who went where and when

But it's still the only attempt so far. -SS

Re: Simple LabVIEW Puzzle Challenge

Darren — Tue, 09 Sep 2008 21:43:52 GMT

Easy enough to add...the data was on the diagram, just needed to add it to the panel:

-D

Message Edited by Darren on 09-09-2008 04:43 PM

Re: Simple LabVIEW Puzzle Challenge

ShotSimon — Wed, 10 Sep 2008 14:33:19 GMT

Darren,

Looks like you're the only one to take the challenge. I really like your very simple brute force approach. When I solved the problem I got it stuck in my head to use toggling back and forth between moving two over and one back. I was playing around with logical checks such as 5 & 10 must go together but gave up since it made the vi very complicated.

I plan on creating another solution that generates all possible solutions as you suggested.

Here is my solution, FYI you solved the puzzle much faster than I did using LabVIEW very impressive.

I will post a new puzzle shortly. -SS

Message Edited by ShotSimon on 09-10-2008 09:33 AM

Re: Simple LabVIEW Puzzle Challenge

ShotSimon — Wed, 10 Sep 2008 15:49:45 GMT

OK LabVIEW puzzle #2 is more challenging and is known as a magic star. I will provide the start to one solution but would like to see someone solve for all solutions.

The rules are similar to a magic square. Using the integers 1-12, each only once, complete the magic star such that each line of four number's sum is equal to the same number 26.

Since this is a harder puzzle I may post a new puzzle before this one is completely solved by someone.

Regards,

-SS

Message Edited by ShotSimon on 09-10-2008 10:49 AM

Re: Simple LabVIEW Puzzle Challenge

Darren — Wed, 10 Sep 2008 20:02:32 GMT

Here's my solution for the Magic Star. It generated 960 solutions. Since there are over 479 million combinations of the numbers 1-12 in the star, it took this VI a couple of hours to run. Again, I used a brute force approach, but this time I was able to calculate every single possible combination (compared to the random combinations I used in the Bridge Crossing problem). Also, credit partially goes to a permutation VI I found at http://www.fafiles.com/examplevis.php that I used as inspiration in calculating my permutations.

The VI is saved in LabVIEW 8.5 this time, since I used For Loop with Break in my solution.

-D

Message Edited by Darren on 09-10-2008 03:02 PM

Re: Simple LabVIEW Puzzle Challenge

ShotSimon — Wed, 10 Sep 2008 20:45:52 GMT

Darren,

That is amazing and very well done. My guess is you are a puzzle master.

I've decided to leave Puzzle #3 open for you to choose...since I can't give away prizes

Try to keep the level of difficultly between LabVIEW Puzzle #1 and Puzzle #2. -SS

Re: Simple LabVIEW Puzzle Challenge

ShotSimon — Wed, 10 Sep 2008 21:25:14 GMT

Darren,

This is known as a magic star order 6 and has 80 solutions. I think the 960 comes about if you count rotated solutions as different solutions, so you are correct.

It is interesting to note some people solve all 80 with paper and pencil using logic no programming. -SS

Message Edited by ShotSimon on 09-10-2008 04:25 PM