Stuck on alternative skyscraper puzzle

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Stuck on alternative skyscraper puzzle

Postby icecream17 » Wed Oct 21, 2020 10:52 pm

Inspired by a Cracking the Cryptic video, I made my own puzzle, with a very easy to guess solution (the first possible sudoku):
123456789
789123456
456789123
912345678
678912345
345678912
891234567
567891234
234567891

(Normal sudoku rules apply)
The digits on the edge of the grid show the first hidden skyscraper on that row or column (in the direction opposite the digit).
I don't know what variant this is called so I named it the "alternative skyscraper" puzzle

So, for example:
Code: Select all
    1 2 8 4 3
  +-----------+
5 | 4 6 5 1 8 | 1
6 | 1 2 9 6 3 | 2
2 | 3 7 8 4 2 | 7
  +-----------+
    1 2 5 1

I started with no digits and got to about here:
Code: Select all
       4     5    6         1       2       3          4     5      6
     +--------------------+--------------------------+-----------------------+
     | 1     2    3       | 456     456     456      | 78    789    79       | 8
  1  | 7     8    9       | 1       2       3        | 4     5      6        | 5
  1  | 4     5    6       | 7       8       9        | 1     2      3        | 2
     +--------------------+--------------------------+-----------------------+
  1  | 25689 16   2458    | 234589  134579  124578   | 35678 4678   2458     | 7
  1  | 25689 167  278     | 234589  13459   12458    | 23568 46     258      | 4
  1  | 23    34   45      | 56      67      78       | 9     1      24578    | 1
     +--------------------+--------------------------+-----------------------+
  1  | 2358  3479 124578  | 2345689 1345679 1245678  | 25678 346789 1245789  | 6
  1  | 2568  4679 14578   | 2345689 345679  145678   | 25678 3467   245789   | 3
  1  | 256   367  2478    | 34589   14569   24567    | 5678  46789  14579    | 8
     +--------------------+--------------------------+-----------------------+
       3     4    1         2       3       1          2     3      2

But I can't figure out what to do next
I'm pretty sure my sudoku has only one solution
icecream17
 
Posts: 1
Joined: 16 October 2020

Re: Stuck on alternative skyscraper puzzle

Postby mith » Mon Oct 26, 2020 4:40 pm

You should be able to do some more with the 1s outside the grid. For example, in r4, you can't put the 1 in r4c6, because it forces 6r4c2, 8r4c3, 9r4c4, broken. Likewise with row 5, which gives a pointing pair in column 5, etc.
mith
 
Posts: 336
Joined: 14 July 2020

Re: Stuck on alternative skyscraper puzzle

Postby Wecoc » Mon Nov 02, 2020 1:35 am

I contacted with Laura Soler, the author of the first puzzle of that type that appeared on Cracking The Cryptic, and I've been playing around a bit with that variant myself for a while.

That variant is called First Hidden Skyscraper Sudoku and is based on a non-Sudoku variant called First Hidden (or Invisible) Skyscraper, which appeared on WSC 2018 (Round 3).

It's possible to make one without given digits, but in that case it's better to have a well-thought break point and path to start with, so it becomes more enjoyable. Luckly some tricks can be used for that, and I can extend on some of those if you are interested.

Now, back on your question, there's something you are not applying and is quite useful on this variant; overlappings.
Notice in the first row r1c8 can never be a 7 because the 8 clue is either 7-9-8 or 9-8.
You can apply the same on r8c8 to eliminate 4, r8c7 to eliminate 5, r8c4 to eliminate 3, r8c1 to eliminate 2... and so on.
I hope that helps.
Wecoc
 
Posts: 77
Joined: 08 April 2019
Location: Girona, Catalonia


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