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Assassin 216

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Børge

Post subject: Assassin 216

Posted: Fri Jul 08, 2011 9:44 pm

Grand Master

Joined: Mon Apr 21, 2008 10:32 am
Posts: 868

Time to make good on my promise in goooders' Special 1, and give Ed some relief.

In goooders' Special 1 I wrote:

I have 9 puzzles with a good SS score spread from 0.93 through 7.02, which both JSudoku and SudokuSolver can solve.
Have to do some analysis of the puzzles first to select which ones to post.

According to Ed one of the characteristics of a good Assassin is that SudokuSolver can solve it in a blink of an eye, and that JSudoku has a terrible time solving it.
The v1 at 1.40 of the upcoming Assassin has exactly this characteristic.

Here the A216 v1. A couple of other easier and/or more difficult versions may follow.

A216 v1

Images:

normalized PS-code:

Solution:

+-------+-------+-------+
| 5 2 8 | 3 9 7 | 4 1 6 |
| 7 6 3 | 4 1 2 | 5 9 8 |
| 4 1 9 | 8 5 6 | 2 7 3 |
+-------+-------+-------+
| 2 4 7 | 9 8 1 | 3 6 5 |
| 9 3 5 | 6 2 4 | 7 8 1 |
| 6 8 1 | 7 3 5 | 9 4 2 |
+-------+-------+-------+
| 3 7 6 | 5 4 8 | 1 2 9 |
| 1 5 4 | 2 6 9 | 8 3 7 |
| 8 9 2 | 1 7 3 | 6 5 4 |
+-------+-------+-------+

EDIT 2011-07-10:
After I posted A216, i tweeted that I had done so and included the hashtags #Sudoku, #Killer and #Assassin.
One result is that Slawabor Henryk'Son mentions A216 and includes a link to it in his #sudoku Daily paper from 2011-07-09.
If you open the bottom collapsible frame, you should see his #sudoku Daily paper from 2011-07-09.

(Archive Note): The image for the final frame has been included; the link to the right of this image no longer worked.

Last edited by Børge on Sun Jul 10, 2011 1:14 pm, edited 20 times in total.

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Børge

Post subject: Re: Assassin 216

Posted: Sun Jul 10, 2011 12:11 pm

Grand Master

Joined: Mon Apr 21, 2008 10:32 am
Posts: 868

A216 v0.5 SS score 0.93 ◄ Select to see the SS score

Images:

normalized PS-code:

Solution:

+-------+-------+-------+
| 1 4 7 | 5 3 6 | 9 8 2 |
| 2 6 3 | 8 4 9 | 1 7 5 |
| 5 9 8 | 1 7 2 | 3 4 6 |
+-------+-------+-------+
| 3 1 4 | 2 6 8 | 7 5 9 |
| 9 7 2 | 3 1 5 | 8 6 4 |
| 8 5 6 | 7 9 4 | 2 3 1 |
+-------+-------+-------+
| 4 3 1 | 9 5 7 | 6 2 8 |
| 6 2 9 | 4 8 3 | 5 1 7 |
| 7 8 5 | 6 2 1 | 4 9 3 |
+-------+-------+-------+

A216 v2 SS score 2.51 ◄ Select to see the SS score

Images:

normalized PS-code:

Solution:

+-------+-------+-------+
| 7 4 1 | 3 9 8 | 2 5 6 |
| 8 5 6 | 2 7 4 | 3 9 1 |
| 3 2 9 | 1 5 6 | 7 8 4 |
+-------+-------+-------+
| 1 3 4 | 8 2 9 | 5 6 7 |
| 2 9 7 | 5 6 1 | 4 3 8 |
| 6 8 5 | 4 3 7 | 9 1 2 |
+-------+-------+-------+
| 5 7 3 | 6 1 2 | 8 4 9 |
| 9 1 8 | 7 4 5 | 6 2 3 |
| 4 6 2 | 9 8 3 | 1 7 5 |
+-------+-------+-------+

A216 v7

for sleepless nights SS score 7.02 ◄ Select to see the SS score

Images:

normalized PS-code:

Solution:

+-------+-------+-------+
| 4 2 1 | 9 5 6 | 3 7 8 |
| 5 7 8 | 4 3 2 | 1 9 6 |
| 9 6 3 | 1 7 8 | 2 5 4 |
+-------+-------+-------+
| 8 1 7 | 5 4 3 | 6 2 9 |
| 2 4 9 | 6 8 7 | 5 3 1 |
| 6 3 5 | 2 1 9 | 8 4 7 |
+-------+-------+-------+
| 1 9 6 | 7 2 5 | 4 8 3 |
| 3 5 4 | 8 9 1 | 7 6 2 |
| 7 8 2 | 3 6 4 | 9 1 5 |
+-------+-------+-------+

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Post subject: Re: Assassin 216

Posted: Tue Jul 12, 2011 5:20 am

Grand Master

Joined: Wed Apr 16, 2008 1:16 am
Posts: 1043
Location: Sydney, Australia

Børge wrote:

give Ed some relief

Thanks! And for taking the next one. I'm still slaving away bug-hunting the next release of SS with Richard. Way behind on catching up with posts here.

Børge wrote:

According to Ed one of the characteristics of a good Assassin is that SudokuSolver can solve it in a blink of an eye, and that JSudoku has a terrible time solving it.
The v1 at 1.40 of the upcoming Assassin has exactly this characteristic.

To be fair to JSudoku, I also look for ones that it can solve easily and SS has a lot of trouble...but it does usually end up that the SS one is the one I can solve or find the most interesting.

Thanks everyone for letting me be the first with a walkthrough!

I couldn't get far with this V1 but fortunately, found some advanced moves (steps 3,8,13) and one trick (step 4). Hopefully, they are all easy to follow. If they are not clear, please let me know. [edit: thanks Andrew!]I know SudokuSolver can't do some of those steps so there must be another way. Finally, thanks for a really tough puzzle Børge!

Start to Assassin 216 V1

13 steps:

Cheers
Ed

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Andrew

Post subject: Re: Assassin 216

Posted: Wed Jul 13, 2011 2:12 am

Grand Master

Joined: Wed Apr 23, 2008 6:04 pm
Posts: 1895
Location: Lethbridge, Alberta, Canada

Thanks for a challenging puzzle, Børge! It may seem surprising but I found this one as hard to solve as the much higher rated goooders' Special 1.

Even though Ed and I worked in the same areas, which are clearly the key ones for this puzzle, we used some very different steps.

Comments of some of Ed's steps:

Rating Comment:

I also used the same "trick" that I used for goooders' Special 1 but it wasn't as powerful this time.

Ed wrote:

Thanks everyone for letting me be the first with a walkthrough!

You're welcome! I was hoping to post my walkthrough yesterday evening but while checking it I found that "I'd seen a hidden single which wasn't yet one" so had to re-work from around step 20. I guess having a "magic button" to show remaining positions for each value, when using a software solver, must be helpful and would have stopped me making that step, but I wouldn't want to have to work with 3x3 grids of small numbers; I really don't know how people can work that way, I'll stick with my Excel worksheet with rows of 9 candidates in each cell.

Here is my walkthrough for A216:

Thanks Ed for correcting my typos.

Last edited by Andrew on Fri Jul 15, 2011 10:45 pm, edited 1 time in total.

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Andrew

Post subject: Re: Assassin 216

Posted: Thu Jul 14, 2011 3:19 am

Grand Master

Joined: Wed Apr 23, 2008 6:04 pm
Posts: 1895
Location: Lethbridge, Alberta, Canada

I found A216 V0.5 much harder than would be expected from calling it a V0.5 and from the SS score. While it started much more easily than the V1, I then had to think hard to make progress.

Rating Comment:

Here is my walkthrough for A216 V0.5:

Maybe I'll try the V2 and even the V7. It's interesting that the V7 has exactly the same SS score 7.02 ◄ Select to see the SS score as goooder's Special 1; however it may well be a lot harder for human solvers.

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Andrew

Post subject: Re: Assassin 216

Posted: Wed Dec 21, 2011 3:33 am

Grand Master

Joined: Wed Apr 23, 2008 6:04 pm
Posts: 1895
Location: Lethbridge, Alberta, Canada

Having done a few other variants, I decided that it was time to have a go at A216 V2.

I actually finished it just over a week ago but then got tempted into trying the V7. I've only now checked my walkthrough and simplified some of the later stages, removing the only step with fairly heavy combination analysis.

Thanks Børge for this variant. It's an interesting cage pattern and was fun to work on; that's not something one can say too often about a V2 puzzle.

Rating Comment:

Here is my simplified walkthrough for A216 V2:

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Andrew

Post subject: Re: Assassin 216

Posted: Thu Dec 22, 2011 2:43 am

Grand Master

Joined: Wed Apr 23, 2008 6:04 pm
Posts: 1895
Location: Lethbridge, Alberta, Canada

When I posted my walkthrough for the V0.5, I wrote:

It's interesting that the V7 has exactly the same SS score 7.02 ◄ Select to see the SS score as goooder's Special 1; however it may well be a lot harder for human solvers.

It certainly was. The "trick" I used for goooder's Special 1 still works for this puzzle, but it's not so useful this time.

I thought that A216 V7 was possibly the hardest puzzle that I've managed to solve (so far?

), although in one respect it wasn't. There have been several very hard puzzles where I got stuck and only came back to them much later. For this puzzle each time that I stopped I managed to make further progress next time I came back to it. However after I managed to simplify my walkthrough, more than I've simplified any previous walkthrough, it probably wasn't quite as hard as I originally thought that it was.

There were several times when, after making breakthrough steps, I omitted some fairly heavy combination analysis steps which I'd originally used. I did quite a lot of analysis on the 24(5) cage at R1C2 and then on the 24(5) cage at R7C8, which I think was necessary so that I could reach the later breakthrough steps. However I've managed to omit the much harder analysis on the pairs of 5 cell cages in N2 and N6.

The 45(9) cage at R3C3 proved to be more important for this puzzle than for the other ones using this cage pattern.

Thanks Børge for a really challenging variant! However that's not an invitation for more very high score puzzles; there are still a lot of those from Ruud's site (available here through the Archive, parts A, B and C) which I haven't yet solved and in many cases haven't yet tried. Maybe next year?!

Rating Comment.:

Here is my simplified walkthrough for A216 V7:

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