Looking for the next step in this Killer Sudoku

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Looking for the next step in this Killer Sudoku

Postby ave » Thu Jan 03, 2019 6:03 pm

puzzle (2).jpg
puzzle (2).jpg (97.76 KiB) Viewed 170 times
I am stumped by this Killer Sudoku. I know a lot of places where two numbers go in two spaces, or what several squares add up to, etc., but I still can't get any further. I would be grateful to hear what someone would fill in next and why. Thank you!
ave
 
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Re: Looking for the next step in this Killer Sudoku

Postby SpAce » Fri Jan 04, 2019 10:17 am

I'm not a killer expert and won't even attempt to solve this further, but there seems to be at least one pretty easy cell. What is the only place for 6 in box 1? It can't be in the 2-cage(6) or in the 8-cage(39) so it must be in r1c3, right?

I don't know how you even dream of solving this puzzle without candidates, though. For me they're a must with all but the easiest killers, but like I said, I'm not very good with killers anyway. (In fact, your question should probably be posted in the Sudoku Variants section and not here.)
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Re: Looking for the next step in this Killer Sudoku

Postby ave » Fri Jan 04, 2019 2:20 pm

Thanks so much for the quick reply! I'm afraid I still don't see why the 39 cage can't hold a 6.

If you have time to explain I'd appreciate it but if you think I should just repost this in Sudoku Variants I can do that--I appreciate the guidance.

I'm sure my solving method isn't the best, but all of the other puzzles at the same level in this book have not been any trouble. I seem to have a block on this one.
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Re: Looking for the next step in this Killer Sudoku

Postby tarek » Fri Jan 04, 2019 8:50 pm

Hi ave,

No time to look at your post. Hatman usually loves these


There is still a pocket of active Killer sudoku solvers on this forum

http://www.rcbroughton.co.uk/sudoku/forum/index.php

tarek
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Re: Looking for the next step in this Killer Sudoku

Postby ave » Sat Jan 05, 2019 8:22 pm

Thank you!
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Re: Looking for the next step in this Killer Sudoku

Postby SpAce » Sun Jan 06, 2019 1:42 pm

ave wrote:Thanks so much for the quick reply! I'm afraid I still don't see why the 39 cage can't hold a 6.

There's only one way to fill 8 cells so that the sum is 39: 1,2,3,4,5,7,8,9. There's no 6 in that list. When solving Killers or Kakuros you should probably have a look-up table with such unique combos, unless you're really good at calculating them in your head (I'm not). Mine came with a sudoku booklet I bought a long time ago, but it shouldn't be hard to create your own as well. I've memorized the combos up to 5 cells (happens automatically after a while since those combos are so common) but almost anything larger than that I would look up.

When solving killers on paper (only way I've ever done it), I use a negative dotting method to mark eliminated candidates (e.g. if candidate 1 is eliminated, I dot the corresponding spot in the cell's 3x3 space). I use the same on regular sudokus but it works especially well with killers, because at first there are many more live than dead candidates. The live candidates are represented by the non-dotted empty spaces in the cells, which might seem hard to read at first, but you get used to it. Then, when there are fewer candidates left and if you need more advanced techniques, you can mark the live candidates more explicitly (I use circles with relationship markers, but you could use regular numbers too if you find them easier to read).

If you're really stuck, SudokuWiki has a Killer solver too:

http://www.sudokuwiki.org/killersudoku.htm
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Re: Looking for the next step in this Killer Sudoku

Postby ave » Sun Jan 06, 2019 2:19 pm

Thank you again! I see how there could not be a 6 in a 39 cage with 8 cells that was all in one box, but 2 of these cells are in other boxes so I don't see why they couldn't use more than one of the same number, thereby allowing a 6 to be included.

And thank you for the tips. It's more fun for me to do these all in my head, and it has worked so far, except for this one...
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Re: Looking for the next step in this Killer Sudoku

Postby SpAce » Sun Jan 06, 2019 3:03 pm

ave wrote:Thank you again! I see how there could not be a 6 in a 39 cage with 8 cells that was all in one box, but 2 of these cells are in other boxes so I don't see why they couldn't use more than one of the same number, thereby allowing a 6 to be included.

Good point. I trusted that the puzzle was conforming with this convention, i.e. that there can't be duplicate digits in a cage even when the vanilla sudoku rules would allow it. I haven't seen a Killer puzzle that didn't follow that convention but I guess it's possible.

And thank you for the tips. It's more fun for me to do these all in my head, and it has worked so far, except for this one...

No problem, and good for you if you can solve them in your head!
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Re: Looking for the next step in this Killer Sudoku

Postby ave » Sun Jan 06, 2019 4:23 pm

Wow. I did not know that convention. I can't believe I haven't run into it a need for it before. It must be the key to solving this one. Thanks so much for your time!
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