Stuck with this one

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Stuck with this one

Postby endyquang » Tue Jan 22, 2019 9:27 am

Hi guys, i'm new to soduko and have been trying to make a little sudoku game
I was able to create unique and as difficult as possible boards
But sometimes there are boards like this one i cant solve. So i get really doubted if those are solvable..
And please explain :)) thanks!
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endyquang
 
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Re: Stuck with this one

Postby SpAce » Tue Jan 22, 2019 5:15 pm

endyquang wrote:Hi guys, i'm new to soduko and have been trying to make a little sudoku game
I was able to create unique and as difficult as possible boards
But sometimes there are boards like this one i cant solve. So i get really doubted if those are solvable..
And please explain :)) thanks!

Hi endyquang! Your board is quite solvable, though not trivial. In fact, I'm wondering... what techniques did you use to get this far? Probably the easiest path to your position already requires two non-basic moves (a Remote Pair and a Skyscraper), and then one more Skyscraper to solve the rest. So, if you solved it this far yourself, you should be able to finish it too (one more non-basic move left, and it's not more difficult than what's been needed already).

Btw, you've missed one basic move: there's a naked pair (16) in box 7, so you can eliminate the 1s from the rest of the box (not really necessary in this case, but it's a good practice to exhaust all basics first). After that we're here, with the Skyscraper move marked up:

Code: Select all
.----------------.--------------.----------------.
|  5     178   3 | 178   2  18  |  4     9   6   |
| b17    1278  6 | 1378  4  9   | c127   5   137 |
|  4     127   9 | 1367  5  136 |  8     12  137 |
:----------------+--------------+----------------:
|  2     9     7 | 68    1  68  |  3     4   5   |
|  36    36    5 | 9     7  4   |  12    12  8   |
|  8     4     1 | 2     3  5   |  6     7   9   |
:----------------+--------------+----------------:
|  9     3-7   2 | 5     8  13  | d1(7)  6   4   |
|  16    16    8 | 4     9  7   |  5     3   2   |
| a3(7)  5     4 | 13    6  2   |  9     8   1-7 |
'----------------'--------------'----------------'

Skyscraper: (7)r9c1 = r2c1 - r2c7 = (7)r7c7 => -7 r7c2,r9c9; stte

In other words, the chain proves that either r9c1 (a) or r7c7 (d) must be a 7; thus we can eliminate all 7s that see both of them (r7c2 and r9c9). After that it's just singles to the end.
-SpAce-: Show
Code: Select all
   *             |    |               |    |    *
        *        |=()=|    /  _  \    |=()=|               *
            *    |    |   |-=( )=-|   |    |      *
     *                     \  ¯  /                   *   

"If one is to understand the great mystery, one must study all its aspects, not just the dogmatic narrow view of the Jedi."
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Re: Stuck with this one

Postby endyquang » Wed Jan 23, 2019 6:14 pm

Thank you SpAce for your explanation!
You are right i got this far by a mistake that i realized later but did not undo back to that mistaken step.
I already knew single, naked, hidden, fish... and some more basic moves but still unheard of many techniques like skyscraper. But i do now
Shamefully i should have learnt more before i posted this. I''m sorry for that

Btw it would be great if i could have you guys play this little game i made and to know your feedback if any.
So here is the url https://endyquang.github.io/nudoku, a progressive webapp so that players can attach to their screen and play like a native mobile app
endyquang
 
Posts: 2
Joined: 22 January 2019


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