Sudoku Demonstration - Skyscraper Technique (Example 01)
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- Опубліковано 27 гру 2013
- As I've continued to grow in my ability to solve Sudoku puzzles, I've also continued to seek out more advanced puzzles to push and challenge myself to learn and understand techniques that are necessary in order to complete "Hard+" puzzles.
Keys to finding and using a skyscraper:
1. Look for two columns or two rows where only two possible candidate exist for a number (ie: Columns 1 and 8 have two cells each where a 3 is possible)
2. Identify if each of the four cells you've spotted is in its own box (ie: as you look at each of the four individual cells, the other three do not exist in the same box)
3. Verify that the four cells form a shape where you can see a "base" (two cells are directly in line with each other; in the same row or same column), and the other two cells up or across from it do not line up directly (these two staggered cells for the "roof tops"). To double check yourself, look at where you think you've spotted a "base" and then look up or across to where the other two cells are. If the other two cells also line up, then you have incorrectly spotted the base. Pick another set of cells that are directly in line with each other and do the same test to verify if the cells across from it are directly in line with each other, or if they are staggered. Once you verify that you can see a base and a staggered top, you've correctly identified the correct aspects of the skyscraper.
4. Now focus on the roof tops. Start at the lowest part of the roof top - from that cell, looking across the row or column towards the highest part of the roof top, look for cells where other possible candidates exist that are visible by both roof tops. Any cells you find can be elimated as possibilities. Do the same thing with the upper roof top now - Look across the row or column towards the lower roof top and find cells where other possible candidates exist that are visible by both roof tops. These can also be eliminated.
NOTE: Whether you look across rows or coumns when dealing with the roof tops will depend on how the skyscraper is positioned on the board. This is why I state in step 4 to look across the row or column where the roof tops are because it will depend on how the skyscraper is oriented. If the base runs parallel to the bottom of your puzzle grid, then the roof tops will sight each other across rows. If the skyscraper is oriented 90 degrees clockwise or counter-clockwise, then the base will be running parallel to the left or right side of your puzzle grid, which means that your roof tops will sight each other across columns.
If anyone watching this video would like to see other examples of this particular technique, let me know and I'll post one or more videos demonstrating it. Or, if you think I did a crappy job and you'd like me to do better, let me know what I can do to improve :).
If you'd like to keep growing in your Sudoku skills, but you're not quite ready for this level, keep practicing beginner to intermediate puzzles until you feel more comfortable and confident to take on new challenges like this and other techniques I'll be demonstrating in the months to come.
I'd like to give a shout out to Tiffany ( / misskity6 . She has some great videos on her channel where she demonstrates beginner to intermediate techniques that are crucial to building a solid foundation.
I'd also like to give a shout out to Angus Johnson for making the game "Simple Sudoku", which is the game I was using to demonstrate the skyscraper technique. Check out his site:
www.angusj.com/sudoku/ - Ігри
Your teaching skills are top notch. You explain everything clearly and logically, and use a step-by-step approach. Exactly what I needed!
Thank you so much Michele! I hope I can upload more videos in the near future :)
Where are you from Michele?
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@@Shuey187 vxHh JJJKNJ
For the life of me, I could not "see" (even after watching other videos) which numbers to take out and which ones to leave in until I watched this one. You are a great teacher!! Thanks a million!!!
Glad to hear that Donald! Thank you for the feedback and support :).
Same here, I was at a complete loss as to WHY this method worked. I get it now, thank you !
Finally !! Someone who explains the skyscraper properly. Thank you.
Thank you so much, and I'm happy it helped! :)
Shuey187: Your series on skyscrapers is one of the best I've seen. Good examples and explanations. Thank you.
Your the first person that I’ve been able to understand an advanced technique from. I have a hard time learning I guess but you really described it straight forward no fluff. I appreciate that soooooo much!
SO good to hear Ashley! Thank you for the feedback and I'm glad it helped! :)
Who else ran to their stuck sudoku puzzles after this video?
:D
Thank you for your clear and concise video. Awesome job!
Finally! I had to re-watch about three times but it's sunk in now. Thank you 😊
I'm glad it was helpful to you Clair! :)
Thank you Shuey for your program recommendation
Very nice demonstration. Short and crisp
Thank you, glad it helped! :)
Short sweet and to the point. I like it!
Thanks beertrain! :)
Wow thanks!! That made it so easily understandable
So glad to hear that, thanks for sharing! :)
@@Shuey187 I just tried this technique on a medium puzzle and managed to get it done with only one mistake when I was averaging 4-6 per puzzle! Thanks!
You explain in such a clear way I almost feel dumb for not having noticed it before hahaha
Hehe, nah! I learn best by seeing, so I'm glad that my video and explanation was able to help you! Thank you so much for the kind words 💗
You explained this complicated technique crystal clearly!!!! Thank you so much!
Thank you for the feedback! I'm happy to hear that it helped :)
Understood and enjoyed, thank you.
Thanks for the nice explanation. I finally got what people referred to as skyscraper. Being new to these terminologies it was a bit confusing so far.
Ahh. Didn't know what was meant by what is "seen" by the cells until you explained it. Wanted to be sure I wasn't confusing myself :) Thanks!
Well done Shuey. I agree with Oumarou.
Sudoku Guy Thank you :)
Wow! Right to the point, very clear, this tutorial is great! Many thanks !
So glad it was helpful, thank you! :)
Thank you for this video! I found a new hobby and im so excited to learn about all these advanced skills! Im watching various skyscraper videos to really hammer it in and I gotta say, yours is the best. Im good now lol
Thank you so much for the support, and I'm really happy that my videos are helping you! :)
Well done
Thank you :)
wow! now I will never get stuck again! thanks!
Thank you for this!!
See on both sides.. like Chanel
thanks a lot for this explanation, very helpful!!
you've made a great video. I loved the explanation.
bye
I'm super excited to find your channel, Shuey! Misskity6 taught me to play sudoku, and I've been hooked for years. I can't wait to learn your advanced techniques. :)
Thanks Scarlett! If you have any specific ideas or questions you want to ask, don't hesitate to let me know :)
Very good. Will do. Thank you! :)
Well done ! Clear explanation !
Thanks Davy! Glad to hear it helped :)
Brilliant - not seen this before - I’m familiar with the X wing and its very similar so that will be very useful, thanks.
Glad to hear it, thank you! :)
Very well explained 👍 THANK YOU SO MUCH 🌹
Thanks for the feedback - glad it helped you! :)
That is so very helpful. Thank you!
My pleasure Stacy, glad it helped :)
absolutely beautiful. Great explanation!! Just like an X-wing. I can't believe I hadn't seen this before!! Thank you.
So happy it helped you out! :)
Nice
Never understood Sashimi Xwings until now. Thanks for the help.If anyone out there has android devices, I highly reccomand Sudoku4ever plus. The hint system is the best I've ever seen in a sudoku app and it allows for four different colouring tools. But nothing beats watching vids like these. XD
+Keith Bellic Thanks Keith! :)
The hint system might be nice, but when it just states this, this and this, with no good explanation it's hard to learn,be specially about the links.
Hey, love the videos on the advanced techniques. What software are you using that allows you to highlight the cells? What software are you using when you are shooting the video that allows you to just show the Sudoku screen without all the rest?
Thanks for the great explanations and high quality videos. Now I'm off to do more puzzles.
+Jeff Ciaccio I use "Hodoku" now (much more robust than the previous software that I was using in this video. The software I use to record the screen is Camtasia Studio.
nice didnnt know of that one
Excellent
Thank you! :)
Does this work also if the "roof top" cells are more than one row apart (vertically in this case)? My logic says it works as long as they're in the same horizontal row of 3x3 columns (example, the roof top to the right moved up one cell), but I'm not sure...
Absolutely! :) If the top right cell was in r4c8 instead of r5c8, it would still be able to see the same "house" of cells that the r6c1 cell can see.
awww thanks Shuey. That's so sweet of you :)
Right on! I am looking forward to getting more people to check out your videos, and hopefully the two of us will be able to get more people into Sudoku in general :)
I am in condition to LEARN MORE! I will go and see if you misskitty will accept my offer ... Facebook here I come.
OK Shuey by watching it more carefully and by watching Example 02, I got it. I know over repeating can drive the geniuses nuts but for the common people it helps and they are the majority;)! Thanks a whale!
My pleasure :)
Correct me if I'm wrong but a number can 'see' itself along its row and column when outside of its own cube and in any direction within its own cube. Thanks for the demo!
good job, actually excellent job, Shuey187
thank you
+Jovo Sedlar My pleasure Jovo, I'm glad it helped :)
Thanks, very informative. Also, what is the puzzle software?
Thank you :). It's listed at the bottom of the video description. I use a newer/better software now though; it's called "Hodoku".
Thanks a lot..
Thanks so much, can you explain if we could also eliminate the 3s in r8c3 and r8c7? Thanks again!
When finding and using skyscrapers, only the "rooftop cells" can be used to eliminate candidates. The X-Wing technique is where you can use all four cells to eliminate candidates. Hope that helps :)
Thank you!!!
Hi Shuey What computer program are you using. I have found that yours is excellent.
Thank you :). It's called Hodoku and it's free (hodoku.sourceforge.net/en/index.php)
for the skyscraper, does the cell out of place from the rectangle shape have to be 1 space up or could it be 2 spaces up?
It can be 1 or 2 spaces (as long as it's in the same house). See this example, starting at around the 5:15 mark: ua-cam.com/video/fBSSJuk885s/v-deo.html
Love your teaching. I am having some trouble with one I am stuck on. Maybe you can show me where I can go from here. If it’s not too much trouble. How can I send you a picture of it?
I'd be happy to help! :)
Send it to johnnyshu@hotmail.com
I have watch most of your video. On very hard puzzles, Extreme puzzles, I'm getting stuck. I have seen things like, "naked triple". on the hint column. Any video on things like that?
Nope, but I could certainly put together some videos of things like that, as well as quads. I'm not sure how soon I could get some videos created, but I'll definitely make a note of this request and do my best to get something up in the months to come! :)
Can you better explain what you mean by the cells seeing other cells? Is there sight include all cells in the row, column, and box that they're in?
Sure :). Review this new comment I posted and see if that helps: ua-cam.com/video/m7DMYKGSYMU/v-deo.html&lc=z232zzwjnqr0gh2y004t1aokgsxlejt0snf2w4pzg0qtbk0h00410.1490738799282011
Here's a brief synopsis as well: Cells can "see" each other if they're in the same house, same row or same column. If two reference cells are not in the same house, then they would either be able to see each other either by row association or column association.
I hope that helps :).
You can also call this a Sashimi X-Wing...you may see it described under that name as well.
What program are you using to play? I have a few, but since I am learning, I would like one that highlights the numbers when I click on one that is already filled in and I can not seem to find a program that does that other than on my phone.
pineapplewafers I actually use a different program now than what I was using in this video; it's called Hodoku. As far as what to use on a phone, I'm not sure since I don't play sudoku on my phone :-/.
well no, i was looking for something on my pc... i will check out Hodoku, thank you :)
I am starting to comprehend these more difficult methods of solving but how in row 6 how did you rule out the 3 in columns 2 and 8 to isolate and find your skyscraper?
I'm not sure I understand what you're asking :(. Are you asking how I got to the point where I found the skyscraper? (Prior to using it to rule out other candidates?)
utHi Huey, I am impressed with your explantions and the computer program you are using. What is the computer program. I'd be happy to give you credit.
Thank you :). Hopefully you saw my reply in the other video where you asked the same question; the program is called Hodoku :).
Unforunately I tried your yrl and it didn't work. Tthanks for trying anyway!
Just Google "Hodoku". The software is free to download and use.
Good video, thanks for sharing!
Where can you find a Sudoku where you can color the cells?
I have a question. At the start of the video we are shown four cells highlighted in green. The right-hand middle block contains the highlighted possibilities 2, 3 and 4. Immediately below this cell is a cell containing 1 and 2. Why can this cell not contain a 3 as a possible number? After all, there are no other definite 3's in that row or column.
There's actually a definite 3 in row 6 (either in r6c1 or r6c9) which rules out the possibility of a 3 in r6c8. A 3 has to exist in either r6c1 or r6c9. And there's also a definite 3 in column 8 (either in r5c8 or r8c8) which rules out the possibility of a 3 in r6c8. A 3 has to exist in either r5c8 or r8c8.
But you could also use X-wing in another square. Those rules would be incompatible ?
At 3:10 you say: "a 3 has to be here or here in this top section..." How is that? I am sure it is true but can you explain why exactly? Thanks!
Sure :). The two columns that form the skyscraper only have a possibility of a 3 in two places (and those cells are highlighted). The cells that form the "top section" will dictate where other 3s can no longer exist, since the two 3s that form the top of the skyscraper are the only two places where a 3 can exist. I hope this helps :).
Awesome, you finally explained in a way I can understand.
So glad to hear, thank you! :)
Does this also apply to the two lower green squares and what threes they can see?
Hi Dave, thanks for the question and for checking out my video :).
In the case of skyscrapers, the only cells that can be used to 100% rule out other cell candidates are the "roof tops" of the skyscraper. The "base" cells cannot be used to guarantee ruling out other candidates. That particular elimination method is only applicable in X-Wing scenarios.
Sudoku methods are a lot like math. They may not always make 100% sense when you're learning them, but as long as you know the rules and when/where they can be applied, you can't go wrong ;)
Hope this helps!
Thank you it does help, and your explanation gives true meaning to method to this madness. It seems to apply to sudoku exclusively.
I know this is an old comment, but I'm replying for the sake of others who are also wondering.
So, to answer your question: no. The upper cells (r6c1 and r5c8) could both be 3, because they are not in the same row/column/block. In this situation, If the upper cells would have been on the same row we would have an x wing and then you can elimante all 3s on the same row (if no other 3s in both columns ofc).
I realize that this is several years old. But where can I et the software that you are using in your tutorial? I'd like to be able to solve sudoku puzzles on my computer instead of on paper. Thanks
I would recommend getting "Hodoku". The software I used in the video is referenced in the description, but Hodoku is what I've been using since then and it's way better :)
Thanks Woody Harrelson 👍😉
lol, huh?
Shuey187 you sound like Woody Harrelson lol ...oh and thanks for the video 👍
What is the program that you use. Where can I go to get it.
It's listed in the description of the video, but I actually no longer use that program. I have been using "Hodoku" for the last couple years: hodoku.sourceforge.net
:)
Thank you
I'm trying simple sudoku software, is there a manual? Couldn't find a way to input candidates...
I would recommend trying Hodoku.
@@Shuey187 Thanks, I'll check it out
Can anyone identify the program being used here as I want similar to help identify patterns
By using colourfill
Thanks
I would recommend "Hodoku"
omg that blew my mind
Can we eliminate #3 in R5C7 as we do in same row??
It may be possible in a later step, but at this point in the puzzle (using the skyscraper to determine more candidates to rule out), the 3 in r5c7 cannot be eliminated because it can't be seen by BOTH rooftop cells.
was this game poorly executed purely for the reason of demonstration? i feel that it is but good info in the demonstration.
hello,
what pc app are you using here?
I don't recall the exact name, but I stopped using it long ago and have been using Hodoku ever since. It's free and really poweful.
I dont get this one, why cant 52 or 53 have a 3? Why must it be in 61 or 81 on the left side?
Re-read the details in the description and see if that helps. The gist is that, because a 3 can only in exist in two places in column 1 (r6c1 & r8c1) and column 8 (r5c8 & r8c8), the "roof tops" of that skyscraper formation dictate what can be eliminated (a 3 as a possibility in r5c2, r5c3 & r6c9) because they are both able to "see" those cells. Again, because a 3 MUST exist EITHER in r5c8 or in r6c1, a possibility of a 3 can be ruled out from any cells that they can both see.
You should explain what it means when you say "... any square that a cell can SEE." I had to rewind and replay parts of the video just to try and grasp what you meant by that terminology. I was literally scratching my head wondering which cells you were referring to in your examples in terms of which squares a cell can "see." Does this refer to an cell in the same row and column? In the same square? I mean technically every cell can "see" all other squares, assuming they had eyes....
Sorry about that. I do give some details about this topic in the video description, but I guess I could've elaborated more by saying something like "Any cells that are visible by BOTH roof tops can be eliminated" (where "visible by both" means any cells that are either visible by row or house). When I say "visible", I mean it in the same sense that cells get eliminated with basic techniques (like when you pick a single cell and you cross reference every other cell that helps rule out candidates). I hope this helps a little more :).
What was that software he used ?
It's listed in the description of the video ("Simple Sudoku")
Doesn't work for a "tighter" distance (don't know how to put it). It has to be connected to the outer columns.
What program is this?
I use Hodoku
Whats the name of the sudoku program?
The one I used in the video is called "Simple Sudoku", but I have since been using Hodoku; it's WAY better!
Shuey187 Thanks!!
What I don't understand is what prevents the 3 from being in both staggered boxes?
I'm not sure I understand the details of what you're struggling with. If you can explain it more, I'll certainly try to help.
Be sure to read the full description again, and then watch the video again - hopefully that'll help :-/
@@Shuey187 I got it, thanks! I was actually looking at a different type of scenario not presented in this video.
Would you say it's less complicated than the Swordfish?
I would ;)
This is explained very well for me, up to a point. I don't quite know what it means to "see" a cell in a Sudoku. I don't understand the process that let the two cells next to each other on the left side of the puzzle be eliminated from the threes. it looks to me like one cell could see the first of the other cells, and the other cell could see the second of the other cells . I couldn't see how both cells could see both of them. Help help!! :) :) :) Can somebody please explain what it means to "see" a cell?? Thanks.
It's funny when I watch my own videos from years ago and I realize how new I was to explaining this, lol. Thank you for the support and patience while you learn the things I'm teaching. Let me elaborate some more on the technique.
Let me first reference some sudoku terminology fundamentals:
1. Each single square in the puzzle where a single number can exist is called a "cell" (there's a total of 81 cells in a sudoku board).
2. Notice that there are 9 "boxes" that each contain 9 "cells" (3x3 squares) - these are called "houses". So if we numbered the "houses", the top row of houses would be "1", "2", "3", the middle row of houses would be "4", "5", "6", and the bottom row of houses would be "7", "8", "9".
3. And there are 9 "rows" and 9 "columns". Every cell exists in a row AND a column. For example, the green highlighted cell at the top left of the skyscraper is in row 6 AND column 1, so it would be labeled "r6c1". And when you want to reference cells that exist in the same row but multiple columns, you can combine the numbers like this --> Example: cell r3c4 and cell r3c6 could be combined as "r3c46".
Looking at the "staggered box shape" that I've highlighted in the video, the two cells in the bottom row could be referred to as the "base" of the "skyscraper". And the two staggered cells at the top could be referred to as the "rooftop" (which looks like it slopes downward from the top right to the top left).
Let's call the cell at the top left "RT1" (r6c1) and the cell at the top right "RT2" (r5c8).
RT1 can "see" all the cells that it shares a house with (house #4), and it can also see all the cells that it shares a row with (row 6). RT2 can "see" all the cells that it shares a house with (house #6), and it can also see all the cells that it shares a row with (row 5).
When we look at which cells both RT1 and RT2 can see, the cells would be:
r5c23 and r6c9
Because RT1 and RT2 can both see those three cells, they can be eliminated as possible candidates since a 3 HAS to exist in either RT1 or RT2.
I hope that helps :)
@@Shuey187 Thank you so much!! That helps a LOT!!
@@Shuey187 I found a skyscraper leaning on its side in a sudoku I was stuck on. I'll see how well I really understood it in a little while. :)
@@Shuey187 WooHoo!!! I guess I understand your explanation, because my sideways skyscraper got me out of my roadblock, and I finished the puzzle. Thanks bunches!!!
@@CynthiaLK So happy I was able to help! Happy Sudokuing! :)
Can you tell me how to add single hints in a cell in a one by one basis without displaying ALL the hints in all cells in Simple Sudoku please ?
Sorry, I don't use Simple Sudoku :( - haven't for years (I use Hodoku)
@@Shuey187 Hi, this video surely looks like you used Simple Sodoku and your description gives a link to Simple Sodoku at the bottom ! You are confusing... Did you use Hodoku for this video ? If yes then... it surely looks like Simple Sodoku.
@@benoit.gerin-lajoie Yep, you're right - I WAS using Simple Sudoku in the video. But what I was saying is that that was basically a long time ago and I don't know :(. I haven't used Simple Sudoku since a few months after that video was uploaded :-/
@@Shuey187 Gotcha ! Thanks. Just found Hodoku and downloaded it. Hope it'll be user friendly...
@@benoit.gerin-lajoie Hopefully you'll like it, it's pretty amazing! :)
I'm confused. You firstly said the 3's could only exist in an x configuration but then went on to state the two 3's were both at the top.
No that's not what he meant. There are 2 possibilities. Either the highlighted cell in the top left is a 3, or the one in the top right. Therefore, no matter which one of those is the 3, there can't be a 3 in cells that are seen by both of the upper highlighted cells.
The 3s in r8c1 and r8c8 for the "base" of the skyscraper, and the staggered cells at the "top" are the ones that you leverage to rule out other possibilities of 3s that the top two cells can "see".
I have always thought of a skyscraper as an "offset x-wing". If this particular example were a regular x-wing, then there would be eliminations of possibilities across BOTH the top and bottom. I have also always been a little confused about how much eliminating can be done, but have finally figured it out.
But in a skyscraper, there is no eliminating done across the rectangular end. Across the base, one of those cells MIGHT have that digit. Or, that digit might not be found in either of the cells of the base.
That means that one (or both) of the cells at the lopsided end have that digit, and the eliminating can be done only from the lopsided end of the skyscraper.
this is simple colouring
I can see why you would think that, but technically speaking, simple coloring and skyscrapers are not the same. Here's a link with more info: hodoku.sourceforge.net/en/techniques.php. Compare "Single Digit Patterns" vs "Coloring" and you'll see what I mean. In the end though, it really doesn't matter what we call these "techniques". As long as everyone viewing them understands how they work and how to spot them, they are useful ;).
If you like sudoku puzzles there's a game called Thermal on Google App Store that combines it with the traditional sliding puzzle. So if you need something more challenging, you can try it here: tinyurl.com/mtpyqfc
(you may even find the sliding puzzle and it's other game modes interesting too! free version without sudoku is here: tinyurl.com/pm9onyq)
maybe you could do a tutorial for the puzzle too?
2021??
Yes! :) I actually have several Sudoku videos that I want to upload soon, so please subscribe and keep and eye out for more :thumbsup:
@@Shuey187 Nice
U totally ignore a sets of 3&4 on the column left of the ones u chosen.. So in fact it inconclusive as to which sets to chose