Can This Puzzle Be Solved By Pen & Paper Only? : Puzzles

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Can This Puzzle Be Solved By Pen & Paper Only?

by Yogi » Thu Jul 28, 2016 11:33 pm

..5...987.4..5...1..7......2...48....9.1.....6..2.....3..6..2.......9.7.......6..
It comes from a list called Top 95 and at least two solvers think it has multiple solutions.
However, with luck you can soon spot 3 corners of a Unique Rectangle and use that to place the 3 & 7 in Box2.
Then with the 3 now placed in Box1, the 1 & 7 are solved in Box 2 and the remainder of the candidates in Box2 are now tied up in a Pair and a Triple.
After that if some progress can be made in Box5 an 'Unsolvable' puzzle suddenly becomes routine.
Interestingly, when I was using Kites to attack Box5, RCB got the same result with an Empty Rectangle.

Yogi: 2017 Supporter; Posts: 349; Joined: 05 December 2015; Location: New Zealand

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Re: Can This Puzzle Be Solved By Pen & Paper Only?

by Leren » Thu Jul 28, 2016 11:53 pm

Andrew Stuart's solver says that this puzzle has at least 500 solutions (it stops counting at 500).

Here are the first page or so of them:

Hidden Text: Show

You can enter the clues into the small left hand grid after clearing it here and then click on the yellow Solution Count button near the top right of the page.

Hodoku also says that the puzzle has multiple solutions.

Leren

Last edited by Leren on Fri Jul 29, 2016 1:48 am, edited 3 times in total.

Leren: Posts: 5119; Joined: 03 June 2012

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Re: Can This Puzzle Be Solved By Pen & Paper Only?

by JasonLion » Fri Jul 29, 2016 1:16 am

I get 905 solutions.

That puzzle is not in top95. However, a very similar puzzle shows up in top95
..5...987.4..5...1..7......2...48....9.1.....6..2.....3..6..2.......9.7.......5..
but it isn't quite the same. For all I know, there may have been earlier versions of top95 that contained invalid puzzles, but the current version has only valid puzzles.

Any puzzle can be solved by hand fairly quickly using focused guessing and a little luck.

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Re: Can This Puzzle Be Solved By Pen & Paper Only?

by Leren » Fri Jul 29, 2016 1:50 am

My solver also found 905 solutions - here they are :

Hidden Text: Show

Leren

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Can This Puzzle Be Solved By Pen & Paper Only?

by Yogi » Tue Aug 02, 2016 5:25 am

Yeah OK I stuffed up again, but you didn't need to bury me in my own muck-up. Either it was a typo, or more likely an error
in the OCR function from one solver to another, but I should have checked more carefully. It was supposed to be
..5...987.4..5...1..7......2...48....9.1.....6..2.....3..6..2.......9.7.......5.. but my remarks are still accurate.
For a supposedly extremely difficult puzzle it seemed to virtually solve itself for the first 20 or so moves.

Yogi: 2017 Supporter; Posts: 349; Joined: 05 December 2015; Location: New Zealand

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Re: Can This Puzzle Be Solved By Pen & Paper Only?

by JC Van Hay » Tue Aug 02, 2016 6:13 am

Code: Select all: +------------------------+-----------------------+---------------------+ | 1 236 5 | 34 236 2346 | 9 8 7 | | 89 4 236 | 89 5 7 | 36 236 1 | | 89 236 7 | 389 123689 1236 | 346 23456 23456 | +------------------------+-----------------------+---------------------+ | 2 13-57 13 | -39(57) 4 8 | 1367 13569 3569 | | -4(57) 9 348 | 1 36-7 36-5 | 3478 2345 23458 | | 6 13578 1348 | 2 379 35 | 13478 13459 34589 | +------------------------+-----------------------+---------------------+ | 3 1578 1489 | 6 178 145 | 2 149 489 | | 4(5) 1268-5 12468 | 348(5) 1238 9 | 13468 7 3468 | | 4(7) 1268-7 124689 | 348(7) 1238-7 1234 | 5 13469 34689 | +------------------------+-----------------------+---------------------+

Skyscrapers{5C14, 7C14} -> -{(57)r4c2, 5r5c6, 7r5c5, (39)r4c4, 4r5c1, 5r8c2, 7r9c25}
11 singles; Pointing{8B4} -> -{8r789c3}; stte

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Re: Can This Puzzle Be Solved By Pen & Paper Only?

by JasonLion » Tue Aug 02, 2016 11:28 am

The purpose of top95 is to list puzzles that require a lot of recursion for a relatively dumb recursive descent solver. That has almost no correlation at all with what a human would consider difficult.

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