Sudoku Demonstration - Skyscraper Technique (Example 04)

[@SudokuGuy]

Excellent Shuey. I like the way you mention what is not a skyscraper and point out that a skyscraper takes up 4 blocks.

[@Shuey187]

Sudoku Guy Thank you, I appreciate the support. I'm starting to wonder if there's a way we could cross promote each other, and maybe even do a tutorial video together :).

[@davidrice9995]

Thank you for an excellent explanation. Now I understand the Skyscraper technique. I've been working on this one for a few days.

[@Shuey187]

+David Rice My pleasure David! Glad the video and info helped :).

[@titushui]

In fact, skyscraper could possibly be located in just 2 blocks instead. The requirement is that the offset U end points must be in the same chute. (However, the elimination could also be done by claiming of locked candidates of conjugate pairs of the base and rooftop points.)

[@theeclecticbanjo]

Thanks for pointing out that second U... I was unsure why it wouldn't have worked until you confirmed it would

[@oumaroudia]

I like that: "base & roof top". Very pedagogical! Thanks!

[@Shuey187]

Right on :)

[@jakesprake]

You don't need the skyscraper to solve it. The two 45s on the left make it a 3 above and 8 below take it from there.

[@henryhache5509]

You mean right.

[@esqueue]

I'm just learning about the skyscraper through your videos. 3:13 column 4 rows 6&7, column 8 row 7 and column 9 row 6. Aren't they a sky scraper? Nevermind, after looking, I notice why you skipped it. There is nothing that can be eliminated. Thanks for your video and I have it a thumbs up as it deserves.

[@Shuey187]

esqueue Thank you :)

[@frankpouyat6767]

Enjoyed your tutorials, would like to know the program you are using. Thanks, Frank

[@Shuey187]

Thanks Frank! The program I used in this video is listed in the description. But the program I've been using since then is called "Hodoku". Check it out and let me know what you think of it :).

[@racapaparaca]

hey, nice videos man! really helpfull! although i have 1 question for you: can you apply skyscraper technique in every sudoku puzzle?

[@Shuey187]

Thank you :). Nope, skyscrapers won't exist in every Sudoku puzzle (just as a lot of other techniques won't appear in every puzzle). The only methods you'll commonly see in almost every puzzle are the basic ones like naked singles, hidden singles and locked pairs.

[@caryg1069]

Nice walkthroughs - I normally use pen-and-paper with scratchpad so this pattern is relatively hard to spot for me, but the explanation is very logical. I did notice the matching pair of "4 5" in R4C9 and R6C9, and that would have also eliminated the 5, but since I tend to overlook stuff like that it's always nice to have a variety methods available. I'm getting started on some tutorial videos as well, which are definitely more "pen-and-paper" oriented. I only have 4 videos at the moment but I hope to have a bunch more in the next few weeks. :)

[@Shuey187]

+Cary G Cool, thanks for the info and I look forward to checking out your stuff! :)

[@caryg1069]

+Shuey187 Thanks man! New video is in processing, should be up soon.

[@titushui]

Just using pencil marks in paper, we must also try to spot out any conjugate pairs in rows and columns and boxes in order to find any advanced logical eliminations possibly found in x-wing, skyscraper, swordfish and so on.

[@aravindsubramaniam4474]

Great Video Shuey! which software do you use?

[@Shuey187]

Thank you! :) At the time of this video, I used "Simple Sudoku" (www.angusj.com/sudoku). But the one I've been using for a long time since then is called Hodoku (hodoku.sourceforge.net/en/index.php)

[@spirituallearning2259]

Im having quite a difficult time understanding this. When theres a valid skyscraper i can easily tell what could be and what cant be a candidate but on your first example in this series you had 3's (c7r5, c8r5) and (c7r8, c8r8) then in the 2nd example tou had 8's (c9r2, c9r3) and in the third example with 9's (c3r2, c4r2) So why is the skyscraper you said was wrong here? With the 5's at (c5r1, c5r2)? Sorry im not really good at wording my questioning.

[@metroid1117]

Hey, I have a question - in the example you presented, wouldn't that mean we can rule out the 5 that is in the same column as your base (middle column, top row)? Great videos by the way, I'm stuck on a couple of puzzles and your material has really helped me out =).

[@Shuey187]

+metroid1117 Thanks for the question and for the compliment - I'm glad my videos are helpful :). I have to apologize to you and everyone else who has supported me thus far... I've promised to upload more videos months ago, and I haven't yet :(. I hope to upload more advanced techniques soon though! :) In response to your question, I can definitely see the logic in thinking that it's possible to rule out a 5 in r1c5, but unfortunately that's not possible, based on the shape that our four primary 5's form. If this shape was an X-Wing (where the four numbers essentially form a box), THEN the 5 could 100% be ruled out from r1c5. But in this case it cannot - the only numbers that can rule out other numbers are the top of the skyscraper (because the base is just a "base" that "supports" the rooftop numbers). I hope this helps - Let me know :).

[@metroid1117]

Ahh I see, that makes a lot of sense. Thanks for the clarification. I watched your other videos and was able to knock out three other puzzles that I've been stuck on for a couple of days, so these techniques really do help!

[@Shuey187]

+metroid1117 Good to hear! Thank you again for the support. I'll do my best to get you some more advanced videos up soon (W-Wing, XY-Wing, Swordfish, etc)! :)

[@metroid1117]

+Shuey187 awesome, looking forward to it =).

[@221191andrei]

Well,I think there are actually 2 skyscrapers formed by number 5 one formed by rows and one by columns and both eliminate another five but indeed the one formed by rows is more likely to be used.I watched your videos and they are great,very helpfull.

[@Shuey187]

Yep, there are actually two of them in this puzzle; I just demonstrated one of them. Good eye though, and thanks for the feedback on my vids! :) I promise to that I'll upload more videos of other techniques soon ;).

[@lexxandera]

I just thought I spotted a different skyscraper... but then it was not? Damn! Why isnt this (row 4, cell 1+6 / row 7, cell 2+6 ) not a scyscraper?

[@Kevin-dp5hv]

You mean column 4, cell 1+6 and column 7, cell 2+6. Columns are vertical and rows are horizontal

[@Shuey187]

Hey Alex, I am SO sorry I didn't reply to your message! I didn't even notice it until today :(. Kevin is correct; it sounds like you misidentified the cells in terms of how you named them. BUT, you are absolutely right in terms of spotting another skyscraper. It's not uncommon to have multiple skyscrapers in one puzzle, and you did a good job of identifying an extra one in this puzzle. Using the 5's in columns 4 and 7, you can eliminate the possibility of a 5 in r2c5 :)

[@davetaylor2449]

This guy does just as good a job at confusing as he does explaining. May be better at confusing, and I would guess if you wanted to receive more comments to make your video to look more engaging, you would do just that. I am a novice and spotted the more obvious skyscraper, there is no way this guy missed it as he said. It's all set up to create more comments to his videos. I from now on will not comment any more, I will just watch this dolts videos and move on and find answers elsewhere. I know this will not be viewable to the public, but i guess there are many many others you do not let be seen either.

[@sven9035]

I was looking at this and thinking exactly the same good to see im not the only one thinking this way :D

[@gok8496]

I'm starting to get it. But, what exactly do you mean by rooftop? ◻️▪️▪️▪️ ▪️▪️▪️🟩 ▪️▪️▪️▪️ ▪️▪️▪️▪️ ◻️▪️▪️◻️ Is the green square what you always eliminate by?

[@Shuey187]

The "rooftop" is formed by the two staggered cells, and you eliminate using both of them (where possible).

[@gok8496]

@@Shuey187 So, is the rooftop a connection of three points?

[@Shuey187]

@@gok8496 The "base" is always going to be two cells that line up, and the rooftop is always going to be the two cells that line up with the base, but don't line up directly with each other (the two rooftop cells are always staggered).

[@geroldbiharie7815]

Great video's. Thx so much. I think that finding a skyscraper among all the little digits is most difficult. When you spot a Skyscraper the technique is easy. But your video's helpt me a lot.

[@Mephistahpheles]

Each of the two skyscrapers take out a 5 from the other skyscraper, so if you use them both at the same time, you can eliminate three 5's. Granted, not particularly important in this Sudoku, but it might be useful someday.

[@irsindhu]

Why don't u take 5 that exist in the first row.why you are moving to the second row

[@Shuey187]

I don't understand what you mean :(... Can you elaborate more? Something I would recommend too is that you re-read the description for this video. It explains the process for finding a Skyscraper, and it will hopefully help with the understanding of why I chose the 5's that I chose. Let me know if you still need help.

[@alanoudalsulaimi2248]

Because in the first row there are three cells where a 5 can be. You can only use rows or columns where the digit can only be in two cells. That's why he went with the second row.

[@rezamiau]

Best Sudoku Tutor. thanks

[@Shuey187]

Thank you so much for the comment :)