## Island - a very elegant logic puzzle

For fans of all other kinds of logic puzzles

### Re: Island - a very elegant logic puzzle

dyitto wrote:It was speeded up by checking if two landcells can be found that are definitely separated by a water line - which was actually quite easy to program.
The second puzzle was solved in 3 hrs. Checking that the solution is unique was at least ready when I looked the next morning.

I'm not very surprised that one takes long because it employs a few observations at the start that i assume are hard to program. As they are all the same number and not connectable with one area of 8 cells, every clue needs at least 2 sections. Then the second observation is that because all numbers are seperated by at least 2 cells, except for one pair so all size 7 islands would have to touch one of those cells.
Those were the 2 ideas I set at the start after placing the first 2 clues in the top left corner. As long as I would make sure all 8s were spread enough and were never 1 or fewer cells apart, I would be sure the logic I used i the beginning would hold.
Para

Posts: 46
Joined: 20 February 2007

### Re: Island - a very elegant logic puzzle

Another one:
Code: Select all
`3;.;.;.;7;.;.;.;..;3;.;.;.;.;.;.;4.;4;.;.;.;2;.;1;..;.;.;2;.;.;.;.;..;.;7;.;.;4;.;.;..;.;.;.;5;.;.;1;..;.;.;.;.;.;3;.;..;2;.;.;.;.;.;3;.2;.;4;.;3;2;.;.;.`

I'll put my program online as soon as the UI is a bit more decent.
evert on the crashed forum

dyitto

Posts: 118
Joined: 22 May 2010
Location: Amsterdam

### Re: Island - a very elegant logic puzzle

simon_blow_snow wrote:I should also try to write a short program to verify uniqueness using brute force. Should not be too hard I suppose?

You can check my solver here:
Last edited by dyitto on Sat Aug 11, 2012 11:33 pm, edited 1 time in total.
evert on the crashed forum

dyitto

Posts: 118
Joined: 22 May 2010
Location: Amsterdam

### Re: Island - a very elegant logic puzzle

Another puzzle:
Code: Select all
`.;.;.;.;.;2;.;.;.7;.;.;.;7;.;.;.;..;.;.;.;.;.;5;.;..;.;.;5;.;.;.;.;..;6;.;.;.;3;.;.;5.;.;.;.;.;.;.;.;..;.;.;.;8;.;.;.;..;2;.;3;.;7;.;.;..;2;.;.;.;.;.;4;.`
evert on the crashed forum

dyitto

Posts: 118
Joined: 22 May 2010
Location: Amsterdam

### Re: Island - a very elegant logic puzzle

dyitto wrote:Another puzzle:
Code: Select all
`3;.;.;.;7;.;.;.;..;3;.;.;.;.;.;.;4.;4;.;.;.;2;.;1;..;.;.;2;.;.;.;.;..;.;7;.;.;4;.;.;..;.;.;.;5;.;.;1;..;.;.;.;.;.;3;.;..;2;.;.;.;.;.;3;.2;.;4;.;3;2;.;.;.`

It is a very nice medium-level puzzle!

Solution: Show
Code: Select all
`3@@@7@@@@#3######4@4#@#2@1#@#@2#@###@@7#@4#####@@5@#1######@3@#@2#@@##3#2@4@32@@#`

dyitto, when you run your solver program on the other five of Para's puzzles as well as stages 3 & 4 of Naoki's, don't forget to tell us how they go.
Last edited by simon_blow_snow on Mon Apr 09, 2012 10:46 am, edited 1 time in total.

simon_blow_snow

Posts: 85
Joined: 26 December 2010

### Re: Island - a very elegant logic puzzle

Did you solve both of my 9x9 puzzles? If one starts with random numbers they probably tend to be medium-level.

As for the other puzzles, my program usually confirms unique solution, and run-times differ from few seconds to 20 minutes to few hours.
evert on the crashed forum

dyitto

Posts: 118
Joined: 22 May 2010
Location: Amsterdam

### Re: Island - a very elegant logic puzzle

dyitto wrote:Did you solve both of my 9x9 puzzles? If one starts with random numbers they probably tend to be medium-level.

As for the other puzzles, my program usually confirms unique solution, and run-times differ from few seconds to 20 minutes to few hours.

Oopsy, I totally did not realise you posting a 3rd puzzle (even though I quoted your 3rd puzzle instead of the 2nd puzzle above). I just solved your 1st & 2nd ones.

You can make it clearer by including a title on top of your puzzle text (e.g. dyitto #1, dyitto #2).

Will have a go at your 3rd puzzle later.

simon_blow_snow

Posts: 85
Joined: 26 December 2010

Previous