Hidden Skyscrapers
(Published on 31. May 2020, 09:04 by glum_hippo)
Inner Sky II
First, the actual puzzle:
And here are the rules: Normal Sudoku rules apply. A little triangle is present between cells if and only if the triangle points from a valid skyscraper clue onto an observed row or column fragment. Triangles can point in any of the 4 orthogonal directions.
What is a skyscraper clue? Imagine all the digits in the surrounding cells as representing skyscrapers with the given number of floors. Thus in row 5, column 5 of the puzzle is a skyscraper with 5 floors. A valid clue would indicate the number of skyscrapers that are visible from the position of the clue when gazing in the direction of the triangle at the remainder of the row or column (shorter skyscrapers are obscured by taller ones).
The negative constraint implied by a lacking triangle is often crucial to the solution path!
Here is an example in which all valid skyscraper clues are marked:
Solution code: Row 4, then column 9, respectively in reading order (18 digits).
Comments
on 5. February 2022, 11:48 by Vebby
Link to solve on Penpa+ with answer check: https://tinyurl.com/2p9b952r
on 6. June 2020, 15:10 by glum_hippo
Re-titled for convention’s sake. Also removed the Hochhausblöcke tag.
on 6. June 2020, 15:08 by glum_hippo
Thank you for sharing that history! Just to add to the confusion: my only encounter with the term ‘hidden skyscraper’ before now was the ‘first hidden skyscraper’ puzzle on CTC which is very different indeed. https://youtu.be/_Q9E_AUdzN0
on 6. June 2020, 07:03 by Richard
Haha, yes that was me (and my best puzzle friend Arvid (Eisbär)). The variant was not invented by one of us, but introduced in the portal with the advent calender 2014 (puzzle ID's 00024N and 00024U) and later it was of course included in SVS. When I saw your first Inner Sky I thought of that as a (slightly) new variant since you only used the borders of the boxes for skyscraper clues. The one here is indeed a true hidden skyscraper. Maybe you can change the name of this one for consistancy reasons...
I think it is virtually impossible to find out if a variant already exists or not and what the name is; the portal alone already consists of 4000 puzzles...
on 6. June 2020, 06:39 by glum_hippo
Ich habe erst heute erfahren, dass Rätsel dieser Art bereits verfaßt wurden unter der Rubrik 'Hidden Skyscrapers', z.B. https://logic-masters.de/Raetselportal/Raetsel/zeigen.php?id=0002DL - ich bitte um Nachsicht!
on 31. May 2020, 16:59 by glum_hippo
missing arrows reinstated
on 31. May 2020, 13:26 by zhergan
Very nice one:) Thanks..
on 31. May 2020, 09:46 by glum_hippo
add tag
