Skyscrapers

I don't understand Skycrapers! Have tried them in the past but gave up and now I'm scratching my head again over those in issue 1. Can anyone give me pointers? Thanks.

Something that might help you is to consider Skyscraper puzzles as if they are Futoshiki. The difference is that they don't put the greater than signs in for you, rather they tell you where the symbols are by other rules.

Suppose we have a 6x6 puzzle. That means the highest number is "6".

Look around the edges. You should find a 1-clue along each side of the puzzle. That means the 6 should go next to it, since only seeing 1 building is the maximum height for the puzzle. What is a bummer is when the 1-clues are in a corner ... less 6's to write in.

Next check the rows and columns where you didn't write a 6. Count how many "away" squares you are from the edge. For example, a square 3 away from an edge with 4-clue cannot have a 6, because at best you would get X<Y<6 and that would only be 3. 2 squares away with a 3-clue works the same (X<6). So you can eliminate this square. If it is still a possibility, cross check it with the perpendicular clues in the same manner.

After doing this ... you might find rows and columns which pair-up, and have only 2 possible squares for a 6. If 2 rows or columns have the same paired-up squares, then you have an X-Wing and you can eliminate those possibilities from other rows/columns. This is the same thing that you do in Futoshiki.

Once you have checked out the 6's ... do the same for the 5's and 4's. For example the square next to a 3-clue can't have a 5.

After this, look for incremental patterns. A row with a 3-clue that has X-Y-6 must increment upward as X<Y<6. If it was a 2-clue instead, you would have X>Y<6. Write in the greater than signs on the grid lines and you are turning the puzzle into a Futoshiki which you already know and love.

That should get you going. Other logic is "front/back" which I am not sure how to explain, but you eliminate numbers by putting them "behind the 6" cause that is the only way the clues will work.

As you do this and write in candidates, it should break down with hidden pairs, single digit, and greater than logic like a Futoshiki does.

Let me know if you need further help. I just finished the SSSS puzzle on Issue 1 page 20 and it was a bugger! You have to do all of this, Ninja Leap, X-Wing, and other things I forgot I did. Not having any 4's didn't help matters either.

Many thanks, Spittledung. The Futoshiki comparison has certainly helped. Have done a couple of the Skycrapers on page 17 and feel like I'm getting into the swing of things now!

Hi Marilyn! Glad you're getting used to the Skyscrapers! I also find these pretty hard going, but enjoy having a go at them! They make a nice change from the standard sudoku variations we see so many of. Don't know whether you have tried the ones on Gareth's blog site? One or two of them are a bit easier for practising on.

Congratulations on completing the SSSS Spittledung. Mine is still a work in progress, ha ha.

Is it me, or are the Skyscrapers in Sudoku Xtra considerably harder than on your blog site Gareth? I managed to do most, but not all of the ones on there, but so far in this magazine have only managed the first three skyscrapers, and just the first skyscraper sudoku. Would it be possible to include a few slightly easier ones at some point? I think you're getting enough suggestions now to keep you going for the next few months or so!!

Sorry about the Skyscrapers difficulty level - I'll make sure there's a couple of easier Skyscrapers next time round! I'm not a big fan of puzzles I get stuck on for a long time, so I can see it might be a bit annoying. They are certainly harder than the earlier ones I posted on my blog, yes, so if you're just getting going those would be a good thing to look at: www.garethmoore.co.uk/category/skyscraper/ (two pages)

Also, Spittledung's suggestion of drawing inequality arrows on them is a great one. The more information you can extract from the clues and put into the rest of the grid where it's easier to apply the better. Once I've placed some digits (and made other pencil marks) I also like to make sure I cross out the edge clues that can't provide any more information than I've already written in - it means when I scan round the puzzle I don't waste time re-checking stuff that's already finished with, and I can focus on the bits that probably matter most.



Edited 1 time(s). Last edit at 12/03/2009 12:10AM by gareth.

Christine, it is NOT just you...

I just completed all the skyscraper type puzzles in issue 1 and the ones in there are much more difficult than Gareth has put out in the past. I felt like he was trying to see how few start numbers he could include.

I can see why Marilyn was geting frustrated. I was doing one of the sudoku type ones and gave up in the middle, thinking "I have other things to get done!" ... but I came back to it later and found the X-Wing linchpin ... so I guess something positive came out of it.

I feel that having these puzzles so hard in issue 1 might turn people off of them, which would be a big shame cause they are fun for me.

Glad it's not just me! I must admit I prefer a challenging puzzle to the ones you can just sit and fill the numbers in without much thought. The harder the puzzle, the greater the satisfaction when you finally get to that one number which opens up the whole puzzle! Mind you, it is nice to be able to get to that stage! I do appreciate though that Gareth has to cater to all levels of puzzlers as we are all work at differnt levels.

I'm not one for all this technical jargon, but now you've explained it I must go and have another look for that X wing and see if I can get any further!

Wow, seems like the level of difficulty of the Skyscrapers is easier in issue 2. Thanks, Gareth! I'm really enjoying them now, and have completed my first SSSS. Yaaa!

Well done Marilyn on completing that SSSS. I agree that the level of the standard ones has been a bit easier in issue 2, but I still haven't managed to complete the samurai one yet! It's one of those that I keep going back to and managing to keep filling in another number or two, so hopefully, with a bit of perseverance, I will get there in the end!

Well once again, this proves how different I am from everyone else...

I can only think it is because I am stressed out at this time, but I did NOT find the Skyscraper Sudokus easier in issue #2. The 6x6 and 8x8 were okay, but I felt the normal ones and the SSSS took way too long for me. It is probably because I am very impatient right now, and if I can't get a puzzle solved in an hour or less I don't want to do it at this time.

... Which brings up a different matter: For future issues is there any way to rank the puzzles by difficulty like using the hourglasses from Sudoku Pro? That way I can I have a reasonable guess on the time it takes to solve a puzzle? I was going to do only one puzzle before bed and it is now 3:30AM! If I had known this one was going to be that difficult I wouldn't have bothered.

So there is my frustration. Now that I have shown it, do YOU have any pointers on how to make these easier? I am getting better at Futoshiki, but now when I see an Inequality Sudoku, Skyscraper Sudoku, or SSSS, I just want to throw it away cause they are starting to feel very tedious for me.

I will aim to add difficulty indicators at some point, but it's feedback like this that's necessary to calibrate the difficulty scale in the first place! Also it's somewhat a debatable point whether a puzzle that takes a long time to solve is actually difficult or simply time-consuming!

In general, I'd say that all of the Samurai puzzle variants are going to be quite time-consuming to solve - so difficult, yes, although I've tried to keep the Calcudoku variants manageable (they could be wayyyyy harder!). For the puzzles in general where there's more than one on a page I've aimed to put the harder puzzles further down the page, reading left-to-right and top-to-bottom.

In my opinion most of the Skyscraper larger than 6x6 are pretty tricky to solve, since there's always going to be a lot of to-ing and fro-ing with the possibilities, so the potential problem then becomes that I label lots of the puzzles as difficult and not much is left to be labelled easy!

What I've tried to do is put in a couple of easier and a couple of harder ones for each puzzle type, so on that basis you can do the half of the magazine you most enjoy. You'd have to do 4 a day of issue 2 to finish it in time for issue 3 anyway!

I guess it can't be easy judging the difficulty of a puzzle as we're probably all on different levels. What could be easy for one person might be difficult for someone else. Regardless, I'd expect the larger puzzles, e.g. the Samurais, to be time consuming particularly if you get to the stage where you need to write in all the possibilities. Personally, I rarely finish a Samurai in one sitting as I'm inclined to be a bit impatient as well. So if I get stuck on the puzzle for too long I move on to another puzzle. Eventually, I go back to the stuck puzzles in the hope of filling in a few more numbers.

What I really liked about issue 2's SSSS was that it was doable without resorting to any of those advanced techniques and that gets a big thumb's up from me! Issue 1's SSSS, however, is still a mess of possibilities that I can't make any sense of !

Not that it's of any particular interest to anyone but myself, but just needed to say that at long last I have completed a SSSS!!! The one in issue 4 so now it's back to issues 1, 2 and 3 to have another go!

Congrats!

As Dave said, congratulations! It actually is of real interest to me - I gauge what puzzles to put in (and at what size) based on people's feedback. Maybe it's time to rest that particular puzzle after 4 issues of it?

No!! It's still one of the ones I turn to first even though I find it quite difficult! Any progress on the Skyscraper Xtra?

NO NO NO Gareth please don't leave it out. I'm with Christine on this one. Please keep it in every issue forever!

Okay, understood!

Re Skyscraper (and Consecutive) puzzle books, I've put them on hold temporarily since I have a deadline on Monday plus some work to do on PuzzleMix, but hopefully in the next fortnight sometime...

Well done on the SSSS, Christine! Gosh, I'm so behind this month, I haven't done any puzzles in issue 4 yet! Best get cracking as issue 5 is just around the corner.

Oh, and another vote to keep the SSSS in!

Marilyn

If you love the SSSS and want more before the next SudokuXtra, or if you haven't tried the SSSS and want a warm-up, try my SSSSSS over at http://www.thegriddle.net/449. It's a Size Six Skyscraper Samurai Star Sudoku.

Also, if any of you use Twitter and tweet about puzzles, today it would be awesome if you would use the hashtag #SudokuSunday so more Twitter users will get to see great puzzles!

Looks like a great puzzle from David - I particularly love the smiley in the middle!

In fact you could have called it SSSSSSS:

Size Six Skyscraper Samurai Star Smiley Sudoku

And of course today is Sunday, so really it's SSSSSSSS:

Sunday Size Six Skyscraper Samurai Star Smiley Sudoku

And the solution is the catchily sibilant: SSSSSSSSS.... or S9, which kind of takes us back to Sudoku 9x9. Instead of "regular" or "vanilla", maybe I should start calling those S9, just to confuse things.

I was actually hoping to see if I could make a SSSSSS with Sudoku X rules throughout, and call it the SxSxSxSxSxS or something like that.

By the way, if you want to try a particularly difficult video game with a title along the same lines here, VVVVVV is amazing.

http://thelettervsixtim.es/

Glad you liked the SSSSSS nonetheless!

ETA: I was thinking of doing a variation with shapes and sums added in - I could post the puzzle on Sunday and give the solution as SSSSSSSSSSSS, or Sudoku Sunday's Shapely Size Six Skyscraper Samurai Star Smiley Sum Sudoku Solution



Edited 1 time(s). Last edit at 03/22/2010 12:06AM by davmillar.

Need Help with Skyscrapers.

I like the easier Skyscrapers. However I have yet to finish a SSSSS. I am a bigger fan of the non-sudoku puzzles - Yajilin & Nurikabe . I tried the one just mentioned (size6S). What am I doing wrong? The 1 hint at the top forces a 6 just below and therefore the only 6 in the first 6 boxes of that column. The next 6 has to be below the 2 in the same column. With the given 5's the only box available for a 5 is two boxes to the left of the new 6. How can there be a hint of 2 to the far left of this 5?

Also generally, is there a method to try when you get stuck? (after looking at all given hints of 1 and 6)

Thanks.

Hi Troy, I have also had a go at this puzzle and came to the same conclusion as you with regards to the 5s and 6s. I rubbed it out and started again and got to the same point again so either we are both doing something wrong or there is a mistake in the puzzle - maybe Dave could have a look at it?
Have you managed any of the smaller skyscraper puzzles in the Xtra magazines? I generally find the ordinary skyscrapers easier than the sudoku skyscrapers, but still find them all quite tricky being relatively new to them - have managed to complete most, though not all the ones in the magazines (but only one of the samurais - yet!).

I don't know whether you have read this thread in its entirety but Spittledung and Gareth have posted a few tips towards the beginning of it, if they are of any use.

Yajilin is a puzzle I haven't got to grips with yet - I take a look and am not sure where to start so maybe that's the next to work on for me!

Not to help in any practical way, but it's great that you're a fan of Yajilin and Nurikabe - they're my favourites too! I'm on a (slow) mission to convert all the world into Yajilin lovers.

It would help (as I might have mentioned before) to put some easier Yajilin in Sudoku Xtra too, to introduce people who aren't familiar. In fact, what a great idea for issue 5, due out in just a couple of days - I'm just going to get out my graph paper and get working on that now then!

Perhaps an easy Nurikabe too... hmm.



Edited 1 time(s). Last edit at 03/23/2010 10:46PM by gareth.

Sorry guys and gals. The bottom left hand two should be a five. Fixing it now!

Just completed Dave's puzzle! Works with a 5. Good puzzle. Thanks, Dave.

Looking forward to Yajilin puzzle(s) in issue 5. The prior puzzles have been great.

Christine, Yajilin is a great puzzle. I had never even heard of it until I saw it in issue 1. With a few things to look at to get started It is a quick learn.

For example, since no to black squares can be together, if you have a clue of 3 with only 5 square available then black squares are 1,3,5. Or often you get a clue of 1 with 2 open squares; but if you fill in one of the choices if will cause a dead end in your loop. Therefore, the other is black. Once you know any filled in boxes, I put a dot in the 4 adjacent squares knowing that my loop will go there at some point.

Also, if you have a dot with only two ways to get in or out (a dot in the corner for example) you can make that part on the loop.

Good luck, Christine. (Once you get it down I recommend the Sudoku and Yajilin book by Nikoli - lots of great Yajilin puzzles of varying sizes and difficulty!) After issue 5, of course.

For anyone:

The rules of Yajilin and a great in progress solution picture.

http://www.nikoli.co.jp/en/puzzles/yajilin/

Thanks for the tips Troy - I am hoping the easier ones Gareth has promised for Issue 5 will get me started - will have a serious look at the ones in the older magazines when I get in from work tonight and see how I get on! I tend to go for number puzzles rather than loop ones but am trying to branch out a bit now!

Dave, have also done the SSSSSS now - a fun puzzle and not too difficult with it being 6 x 6.

I think I put easier ones in issue 4 too? The 6x6 ones are much easier than the 7x7 ones, and I made sure the first 6x6 and to an extent the second 6x6 in issue 5 are easy enough too... I hope.