Tutorial #75. The skyscraper A detailed look.

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#sudoku #learn Sudoku #Sudoku guy
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The skyscraper takes time to spot but can be very valuable in eliminating small numbers.
An understanding of strong (conjugate pairs) and weak links is important.
If you learnt something for this video please give me a thumbs up under the video.
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Shehu Mayaki sent me this summary. Thanks Shehu
SUDOKU SKYSCRAPER TECHNIQUE
1) 1 Candidate forming a conjugate pair (i.e: only 2 cells in a row or column) in 4 separate cells which lie in 4 different blocks
2) The 4 cells are connected by 2 strong links (conjugate pair) and 2 weak links on any 2 opposite sides and must lie parallel to each other
3) The links must be in the order of strong - weak - strong
4) One side of the resultant parallelogram must be slanted while the remaining sides are flat (the 2 points of the slant must be on 2 rows or 2 columns)
5) The slanted side is said to be the roof of the skyscraper, while the opposite side of the slant is the floor
6) The higher side of the slant (roof) forms one corner while the lower side of the slant (roof) forms another corner (Note: no link, either strong or weak, between the 2 ends of the roof!)
7) The two ends of the floor form the other other 2 corners
8) There are 2 types of eliminations that can be made: a) on the roof of the skyscraper and b) on the skyscraper walls using X-wing diagonals
9) Eliminations on the roof will be the skyscraper candidates that see both ends of the roof (i.e. the candidates on the same row or column of the roof and also in the same block as the lower end of the roof)
10) The second set of eliminations will be those aligned with the diagonals (X-wings) of the skyscraper candidate, using the X-wing rule!
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Опубликовано:

28 июл 2024

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Комментарии : 117

@RonMaxfield 2 года назад

Robin, have you ever been a school teacher. You appear to me as a math, school teacher. If you were a teacher at one time you had to be the best teacher in the entire School. You are witty, you get the point across very well and you have the ability to hold our attention. Thank you very much for all these videos they have helped me immensely. I am hooked on Sudoku. I can't go to sleep at night without playing at least three games of Sudoku. Thank you! 🤗😀🤗

@SudokuGuy Год назад

Hello Ron. You have made my day. Yes I was a teacher for over 30 yrs. So glad you found my site."the most popular site online to learn sudoku" Please share with others, subscribe and click the bell by the subscribe button. Have fun as you learn step by step how to solve.You will find all my videos here ru-vid.com/show-UCd8JaOdfEWcJOtwG6YayW0w ru-vid.com

@SmartHobbies 2 года назад

Great video Robin. I love the shoutout to the Swami. You both have taught me so much about Sudoku. One note of caution about skyscrapers. The strong weak strong link relationship only tells us that at least one of the roofs is true so we can make eliminations, but they could both be true as well. You seem to imply at the beginning that you can assume that one of base numbers has to be true so we can make eliminations along the base column or row and that’s not completely accurate. In your example with the 3’s in row 7, we could only make eliminations along row 7 after seeing the effect the roof had on the 3’s in the upper rows, not before. I hope that makes sense.

@SudokuGuy 2 года назад

Thank you for your comment. Yes you have a point and i should have mentioned this.

@SoRTs6233 2 года назад

I was working on a puzzle and I knew there was a skyscraper there but I didn't know what to do. After this tutorial, I went back to the puzzle, used your technique and got it solved! Thanks Robin, great work. Cheers

@SudokuGuy Год назад

So pleased to hear that....congratulations. Please tell others about my site.

@shehum 2 года назад

Aw! Wow! I've finally added skyscraper to my repertoire of solving techniques! Not that I have many to begin with! Apart from the basics, I only have X-wings and Unique Rectangles (URs) to work with. But now thanks to this tutorial, Robin, I have another technique. Can't wait to recognise and try it out. See my notes from this tutorial: SUDOKU SKYSCRAPER TECHNIQUE 1) 1 Candidate forming a conjugate pair (i.e: only 2 cells in a row or column) in 4 separate cells which lie in 4 different blocks 2) The 4 cells are connected by 2 strong links (conjugate pair) and 2 weak links on any 2 opposite sides and must lie parallel to each other 3) The links must be in the order of strong - weak - strong 4) One side of the resultant parallelogram must be slanted while the remaining sides are flat (the 2 points of the slant must be on 2 rows or 2 columns) 5) The slanted side is said to be the roof of the skyscraper, while the opposite side of the slant is the floor 6) The higher side of the slant (roof) forms one corner while the lower side of the slant (roof) forms another corner (Note: no link, either strong or weak, between the 2 ends of the roof!) 7) The two ends of the floor form the other other 2 corners 8) There are 2 types of eliminations that can be made: a) on the roof of the skyscraper and b) on the skyscraper walls using X-wing diagonals 9) Eliminations on the roof will be the skyscraper candidates that see both ends of the roof (i.e. the candidates on the same row or column of the roof and also in the same block as the lower end of the roof) 10) The second set of eliminations will be those aligned with the diagonals (X-wings) of the skyscraper candidate, using the X-wing rule! There! Hope I made sense!!

@SudokuGuy 2 года назад

FANTASTIC summary. I will add it to the description underneath the video and give you credit.

@shehum 2 года назад

@@SudokuGuy Wow you've made my day, Mr. Robin! Thanks a lot for also making me know that I'm on the right track.

@wood_pecker_ 2 года назад

@@SudokuGuy you are so kind sir ❤️❤️❤️

@terrybolerjack197 2 года назад

Thank you Robin! I always find value in your videos!!

@SudokuGuy 2 года назад

You are so welcome!. Thank you for your support. And thanks for telling others. Roibn

@cakemashers1816 2 года назад

Thank you! I didn’t know about this technique. It’s very helpful as it seems to available quite often. You have a great aptitude for teaching and with your winning personality, you remind me of the Bob Ross of Sudoku. You are beloved in our household.

@SudokuGuy Год назад

Thanks. You are now on your way to enjoy solving sudoku. Watch each video in order as they take you step by step to learn procedures and how to watch for answers. Master the easy puzzles first by watching lessons 1-12. So glad you found my site."the most popular site online to learn sudoku" Please share with others, subscribe and click the bell by the subscribe button. Have fun as you learn step by step how to solve. For a list of videos go here: ru-vid.com/show-UCd8JaOdfEWcJOtwG6YayW0w sudokuguy.com

@DanaHuseby1017 2 года назад

Thank you for taking the time to explain the process so clearly!! 😁

@SudokuGuy 2 года назад

You are so welcome! hang in there, You can do it. master one level at a time. Each video will take you a step further and revise what has already been covered, particularly procedure.

@povrtsux1 3 месяца назад

LOVE IT. GOD BLESS YOU FOR ALL YOUR HELP !!!

@SudokuGuy 3 месяца назад

Gee !!! thanks so much for your support. Please tell others about my site. ru-vid.com/show-UCd8JaOdfEWcJOtwG6YayW0w

@DuyNguyen-pb4pw 2 года назад

This just singlehandedly solved the puzzle i was stuck on. Thank you so much for showing this technique!

@SudokuGuy 2 года назад

Glad it helped! Duy. So glad you found my site."the most popular site on line to learn sudoku" Please share with others, subscribe and click the bell by the subscribe button. (It’s FREE) Have fun as you learn step by step how to solve. Below is my home page with all the videos listed. ru-vid.com/show-UCd8JaOdfEWcJOtwG6YayW0w

@danivaljean9073 Год назад

divino, genio, te adoro! Gracias por tu dedicación!!!!

@SudokuGuy Год назад

So glad you found my site."the most popular site online to learn sudoku" Please share with others, subscribe and click the bell by the subscribe button. Have fun as you learn step by step how to solve. For a list of videos go here: ru-vid.com/show-UCd8JaOdfEWcJOtwG6YayW0w sudokuguy.com

@bookaholic1431 2 года назад

Thank you so Much for the helpful tutorials, Mr. Robin!🙏

@SudokuGuy 2 года назад

My pleasure! So glad you found my site. “the most popular site online to learn sudoku” Please share with others, subscribe and click the bell by the subscribe button. Have fun as you learn step by step to solve. You will find all of my videos below. ru-vid.com

@initiativeplaytherapy88 Год назад

I almost never see classic X wings, but I see this pattern. All. The. Time! Definitely going to use this one. Thanks.

@SudokuGuy Год назад

Enjoy! Initiative play therapy. So glad you found my site."the most popular site on line to learn sudoku" Please share with others, subscribe and click the bell by the subscribe button. Have fun as you learn step by step how to solve. ru-vid.com/show-UCd8JaOdfEWcJOtwG6YayW0w sudokuguy.com

@prabhattomar4587 2 года назад

Thanks for explaining and clearing doubts. Sky scrapper is an excellent method to solve the puzzle.

@SudokuGuy 2 года назад

Happy to help. Prahbat. So glad you found my site. “the most popular site online to learn sudoku” Please share with others, subscribe and click the bell by the subscribe button. Have fun as you learn step by step to solve. You will find all of my videos below. ru-vid.com

@gardenbee583 2 года назад

You are a great teacher, Robin Sir.😀🙏

@SudokuGuy 2 года назад

Wow, thank you

@user-gi8fs6xl5o 2 года назад

Saving in my playlist, I will watch after working hours

@SudokuGuy 2 года назад

Great Z. Sometimes watching more than once helps too.

@alwyalbiansyah 2 года назад

best teacher i've ever had

@SudokuGuy 2 года назад

Thanks ichsan. So glad you found my site. “the most popular site online to learn sudoku” Please share with others, subscribe and click the bell by the subscribe button. Have fun as you learn step by step to solve. You will find all of my videos below. ru-vid.com

@itsbouquet5276 2 года назад

Great Teacher Ever!!😊🥳💖

@SudokuGuy 2 года назад

Thank you! 😃 So glad you found my site. “the most popular site online to learn sudoku” Please share with others, subscribe and click the bell by the subscribe button. Have fun as you learn step by step to solve. You will find all of my videos below. ru-vid.com

@iamshemyo6563 2 года назад

Thank you so much. This technique has helped me to think better when solving the puzzle.

@SudokuGuy 2 года назад

Glad it helped lanshe. So glad you found my site. “the most popular site online to learn sudoku” Please share with others, subscribe and click the bell by the subscribe button. Have fun as you learn step by step to solve. You will find all of my videos below. www.sudokuguy.com or ru-vid.com

@FaithApologetics2.0 2 года назад

Robin sir is the best sudoku teacher in the world I think Sudoku guy is amazing If I press a video of sudoku guy I can't press back until the video end Fabulous work May God bless you with good health and strength 🔥❤

@SudokuGuy 2 года назад

Gee!!!! thanks....you have made my day!!

@FaithApologetics2.0 2 года назад

@@SudokuGuy yee 😍❤

@78tag 2 года назад

In the upside-down roof, you stated that the 3 "inside the house" couldn't see the 3 in the corner of the roof (because it is in the same block) so it couldn't be eliminated. Did you mean to say it couldn't be eliminated because it couldn't also see the other corner that wasn't in the same block? I'm not trying to be a wise guy here - I am finally at the point where I can sometimes use the X-Wing to solve puzzles that can't be solved by pure elimination. I only halfway understand the elimination process of the X-Wing and your explanation of the Skyscraper is really helping my progress. Thanks much. EDIT: when I went back to that explanation, I caught the part about it "needing to be outside the block AND it can't see the bottom corner because it isn't in the same block (meaning it isn't in the same row/column). I was going to delete this comment when I made that realization but then I thought maybe some else might get something from my query.

@SudokuGuy 2 года назад

Thanks for sharing.

@a_son_of_light 4 месяца назад

Question for Robin: Reference: time mark 14:07 to 14:22 My thinking was as follows: The 3 inside the building (R4C6) CAN "see" the 3 in the left (bottom) corner of the roof (R4C4) (because it's in the same house), but it CANNOT "see" the 3 in the right (top) corner of the roof (because it's NOT in the same house), so it CANNOT be eliminated. (same house = common row, column, or block). Any 3 in this puzzle that can interact with the skyscraper would have to be able to see both corner-of-the-roof 3's or corner-of-the-floor 3's in order to be eliminated. It's two different ways of looking at it, but I don't understand why one would assume the 3 in R4C4 to be real rather than the 3 in R4C6. If R4C6 is the real 3, it's a very different outcome, so shouldn't that possibility have been included and explained in the video? I'm confused. I would appreciate any corrections to my understanding. Thank you.

@78tag 4 месяца назад

@@SudokuGuy - I am leaving these conversations now. The time I was spending on puzzles is consumed with thought on what Biden/Obama are doing to the country and what, if anything, we can do about it. It was nice knowin' ya.

@lfavila50 2 года назад

Very Nice. Thank you!!!!!

@SudokuGuy 2 года назад

Thank you too! and for your support. Luiz

@kskaliprasadkotagal6468 2 года назад

Thank you for your efforts teach. Today I am very happy and clear about skyscraper. Thank you again

@SudokuGuy 2 года назад

You are most welcome

@Ryannaut_g 8 дней назад

Thank you Sudoku Guy!

@SudokuGuy 6 дней назад

My pleasure. There is always something to learn . Enjoy as you progress through the tutorials. Robin

@niniacresiannjalagat5386 2 года назад

You're so great sir!

@SudokuGuy 2 года назад

Thank you kindly! So glad you found my site. “the most popular site online to learn sudoku” Please share with others, subscribe and click the bell by the subscribe button. Have fun as you learn step by step to solve. You will find all of my videos below. ru-vid.com

@yousraben9417 4 месяца назад

I finally understood it, thank you ❤️

@SudokuGuy 3 месяца назад

Glad it helped! You are on your way now to try harder puzzles. They get harder as you go up in numbers. However on the way I revise and introduce new techniques for solving Robin

@AbdulMumin0 2 года назад

You are AWESOME!

@SudokuGuy 2 года назад

You too!! Abdul You can do it...nothing like practice and looking at my tutorials and lessons. So glad you found my site. “the most popular site online to learn sudoku” Please share with others, subscribe and click the bell by the subscribe button. Have fun as you learn step by step to solve. You will find all of my videos below. ru-vid.com

@BinarySec 2 года назад

love your videos 😍😍❤️❤️

@SudokuGuy 2 года назад

Thanks Lots to learn eh! So glad you found my site. “the most popular site online to learn sudoku” Please share with others, subscribe and click the bell by the subscribe button. Have fun as you learn step by step to solve. You will find all of my videos below. www.sudokuguy.com

@junkmailfolder5600 2 года назад

Great explanation professor! 🙂

@SudokuGuy 2 года назад

Happy to help! Love you name! So glad you found my site."the most popular site online to learn sudoku" Please tell others, subscribe and click the bell by the subscribe button. Have fun as you learn step by step how to solve. You can view all of my videos here: ru-vid.com/show-UCd8JaOdfEWcJOtwG6YayW0w sudokuguy.com

@osvaldobenavides5086 2 года назад

Thanks!

@SudokuGuy 2 года назад

No problem! osvaldo.

@jamesgoacher1606 2 года назад

That was an interesting and absorbing video. I accumulated questions as you wen along (of course) and you answered as you progressed. The first thing that I queried that became clearer later way when you said a candidate was not I paused the vid and looked at it as if it was, that type of thing etc. The last puzzle was good and I am glad you showed it. I first saw 3 as a possibility then the 8s. Pleased with myself. The remaining question that I have to ask is in which order do you apply these "rules" there were a couple of places where the solution was evident in another, simpler manner. and I tend to avoid cluttering up the puzzle with candidates until the more straightforward methods are done. Fot instance I slice and dice with the numbers 1-9 first, then I start with the more creative ways.

@SudokuGuy 2 года назад

Hello James. Yes I have a step by step procedure. however If I see something that can be useful re getting another number or more I will use it. Beginners need to learn a procedure. It is the teacher in me! You appear to be progressing and that is great. congratulations. Robin.

@jamesgoacher1606 2 года назад

@@SudokuGuy Oh Dear! I have been doing them since they started to appear in The Guardian some twenty years ago I suppose. They should be included on the list of Class-A Drugs. I have fix of about half a dozen each morning half/half Classical/Killer although I do not get very far with the Killer past Moderate. To be honest the solving "Rules" for 'Killer' have never gotten fully into my head. Even an 'Easy' one can take an hour but strangely if I break off for some reason at a stuck phase when I come back it sort of leaps out. It must be difficult to do the teaching videos I assume becase your inner head is a dozen jumps ahead of your Marker Pen. :-)

@amithaabeykoon7309 2 года назад

thank you sir

@SudokuGuy 2 года назад

Most welcome. there is always something to learn. eh!

@clinex3223 2 года назад

Men you are always great thanx to you

@SudokuGuy 2 года назад

I appreciate that! clinex So glad you found my site. “the most popular site online to learn sudoku” Please share with others, subscribe (FREE) and click the bell by the subscribe button. Have fun as you learn step by step to solve. You will find all of my videos below. sudokuguy.com ru-vid.com

@vitormonticelli405 Год назад

Can you apply skyscraper if the roofs are in different blocks? (For example, at 3:01 if the 8 that is on Row2 Column3 was on Row4 Column3 instead of Row)

@SudokuGuy Год назад

Yes you can providing the wall are parallel.

@MrElBenno 2 года назад

Hey Robin, another good video! Thank you! did u use the german word 'kaputt' for elimination? :D How do you know that, would interest me :D

@SudokuGuy 2 года назад

I studied German and my dad used to use this word.

@MrElBenno 2 года назад

Oh that is very interesting :D So i was right that you used this word, one of your funny thing, that makes me laughing :D

@a_son_of_light Месяц назад

@14:10 I believe you misstated why the three in r4c6 cannot be eliminated. You say "this 3 here, it cannot see this 3 because it's in the same block." I would say "it can see one corner of the roof but it cannot see the other corner of the roof, therefore it cannot be eliminated."

@SudokuGuy Месяц назад

Thanks for your comment. Robin

@a_son_of_light Месяц назад

@@SudokuGuy I didn't mean my previous comment as criticism; I'm not an expert as you are. I just wanted to know if I had missed something in my learning sudoku, because I thought that being in the same house was the requirement for one number "seeing" another.

@noraromaguera4737 2 года назад

Your like the sudoko god

@SudokuGuy 2 года назад

Really Thanks,

@hannahjewell8363 2 года назад

Where do u explain weak link surrogates?

@SudokuGuy 2 года назад

Go to my channel page sudokuguy.com and click on tutorials and scroll down to tutorial 68 and 70 This may help. Robin

@GFlCh 3 месяца назад

At 22:55, you've just placed the "Big-5" in the left corner of the Roof, and are getting ready to eliminate the "Small 5" of the "5/9" at the right corner of the roof at "Row-2/Column-8". Notice, there is also another "5/9" in the same row, at "Row-2/Column-9". But there are no "Strong-Links" that you usually draw in Red to represent the Walls of the Skyscraper. So, how did you choose the "5/9" in "Column-8" instead of "Column-9" for the right corner of the roof?

@SudokuGuy 3 месяца назад

I hope this helps. Yes your point is well taken, but this was a small section to show a technique.

@andrewan8855 Год назад

for the weak link how can we so sure that if one is not 8, other end of weak link must be? on the bottom row, can we have not 8 and not 8 for the weak link? where bottom row 8 is at other column? i am confused about it has to be a X wing. i mean there is a weak link.

@SudokuGuy Год назад

I suggest keep watching. Sorry Andrew. All the best. So glad you found my site."the most popular site online to learn sudoku" Please share with others, subscribe and click the bell by the subscribe button. Have fun as you learn step by step how to solve. For a list of videos go here: ru-vid.com/show-UCd8JaOdfEWcJOtwG6YayW0w sudokuguy.com

@sgarcata 8 месяцев назад

Can the ends of the roof exist in the same block? the same shaft?

@SudokuGuy 8 месяцев назад

Sorry no. The corners of the skyscraper are always in a different block Try looking at other tutorial/lessons on my site which cover the skyscraper. Robin

@GreenMeansGOF 10 месяцев назад

I don’t understand the X-Wing step. What is stopping both roof corners from being the candidate?

@SudokuGuy 10 месяцев назад

I am not sure what you mean however in the sky scraper the roof must always be on a slant. Please le me know the min/sec in the video you are referring to.

@GreenMeansGOF 10 месяцев назад

For example, at 17:36, why does row 4 column 5 have to be a 5? Why can’t row 4 column 9 be a 5?

@dailydribble 2 года назад

Gosh as a new player, just got a book and the first group of lessons is "shadows" and I think the book is wrong, being here goes: Multiple shadows grid 1-9 Hstrip and A-i V strip ok now told to put 1's in G-5 and D7 and the shadow will only leave i-9 for a 1 but I see i-9 and h-9 for a 1 what am I missing it is the same as no same number in the block or + ;) looked for your recent clip to ask

@SudokuGuy 2 года назад

Hello Deborah, I think you need to get another book as what you have seems to me to be very complicated.

@dailydribble 2 года назад

@@SudokuGuy thanks so such a prompt reply what a pleasure, yes what I don't understand is the shadow, and X in a cell and an empty cell (ugh) here is the properties: If a cell X is empty, then no number in the shadow of X can be entered into X, If a cell X contains a number , then that number cannot fill any other cell in the shadow if X, it seems alright but then tricky with what no number just pick any blank cell. Lucky I came across you channel, thank you so much Or ever heard of shadowing?

@christopherjamescj1331 Год назад

25:08 why cant i assume that three can be in both the upper right block and upper middle block

@SudokuGuy Год назад

Column 2 is Ok but column 6 will not work as it has 3 cells with a small 3 which means it is not a strong link. I hope I have understood your question Robin

@christopherjamescj1331 Год назад

@SudokuGuy no i meant why cant there be 3 in column two and colum five

@christopherjamescj1331 Год назад

4:42 why cant there be 8 in left lower block

@menjobleeko4135 2 месяца назад

So you would have to find four blocks without that big number, or it wouldn't be there.

@SudokuGuy 2 месяца назад

Yes Thanks for sharing. Robin

@christopherjamescj1331 Год назад

4:39 why are you assuming that the bottom left of sky scraper is the real 8

@SudokuGuy Год назад

Thanks for your question. The best way for me to explain is to ask you to look at tutorial #62 and #63. Also this is not a real puzzle but a demonstration of a technique Yes the base could be either one corner being an 8 ot the other corner being 8. It depends on What happens if this was a complete puzzle. Robin

@shamabole7803 2 года назад

I thought the top of the skyscraper had to hinge on CPs, But 235 isn't. 15:20

@SudokuGuy 2 года назад

CP's ??

@shamabole7803 2 года назад

@@SudokuGuy Conjugate pairs

@SudokuGuy 2 года назад

See my comment below. Thanks for your comment.

@christopherjamescj1331 Год назад

Why cant hothbthebipper points of skyscraper be real sixes here, @11:45 . The elimination using roof is crystal clear but the one using diagnals seems unclear . U said for argument sake assume if it is a real six but it seems like u r ruling out the other possibility

@SudokuGuy Год назад

I suggest you look at my tutorials # 62 -3 as these show the diagonal of an Xwing. A skyscraper has similarities to an X wing.

@austinbrian4082 2 года назад

You can go ahead and throw that thang on 1.25x

@SudokuGuy 2 года назад

Not sure what you mean. Hang in there.

@lory6605 2 года назад

Where you ever a teacher?

@SudokuGuy 2 года назад

Yes it was my profession for 330 yrs.

@MrChrisdube 2 года назад

You keep saying "if this became a real "pick a number" then the one in the same row or column can't be that same number.1 You never seem to specify how you know that number that you use hypothetically IS the actual number.

@SudokuGuy 2 года назад

This is deliberate. I am just explaining a rule. Hope this helps.

@78tag 2 года назад

He is just saying (to save the time solving the puzzle) that as you go you might narrow one of those corners to the one number you were looking for.

@chiowastaken 2 года назад

who still play sudoku in 2021 ?

@SudokuGuy 2 года назад

Me!!!! So glad you found my site. “the most popular site online to learn sudoku” Please share with others, subscribe and click the bell by the subscribe button. Have fun as you learn step by step to solve. You will find all of my videos below. ru-vid.com