Crack Hard Sudoku Puzzles With the Skyscraper Pattern

Lesson #13: Here are two examples of the skyscraper pattern, one where the base is across a row, and the other when the base is down a column. I go through the logic of how this works. You can use this technique in your chest of tools to solve harder sudoku puzzles. I hope you enjoy!

[bobadams]

I really appreciate the added explanation on this “next level” tool to solving puzzles. I know it may be too draw out for some, but there it maybe the only way I and others will get it.

[victorpitigliano]

but at 3.06 if the 7 in H2 is false, the 7 in H6 might be true so the 7 in H7 isn't obligated to be true. I don't understand

[ertanyesildas]

Hello, i've listened and tried to learn this from videos, and even read on internet.
But this video is finally where i understand it. Thank you 🙂

[reethujha]

Thanqq... Tried solving a sudoku which was looking impossible to solve, using this method...and my sudoku was solved in few seconds... It's awesome...

[zacharylauinger]

Great video! This was the trick i needed to solve my sudoku

[kikilynn]

Thanks for the video? Do the 4 points that make up the skyscraper have to be in separate blocks for this to work?

[chaosmester]

1st example: both top-7's could be true (A7 and B2), with row H having a 7 in column 6. The argument holds when reasoning from False > True > F > T, but fails in the T>F>T>F case. I.e. if A7 is False then B2 is True, but the reverse doesn't hold. Or am I missing something? The problem is that H2 and H7 don't have a strong link because of H6.
EDIT: there *is* a strong link once you identify the matched 2-7 pair in H2/H7 (which eliminates all other 7's from row H). But you do that only afterwards. So yes, the skyscraper argument eventually holds, but only if you had presented it in the right order.

[truemomo]

Great video, thank you! Just a question regarding the “roof” of the pattern.

n first example, why couldn’t c7r1 & c2r2 both be sevens? They don’t share the same row?

In the second one, c4r5 & c5r3 could both be threes?

[jeancerrien]

Thank you for the nice explanation. I liked the second example better: some of the logic you applied at the end of the first could have been applied before you invoked the skyscraper.

[akiladevi]

I learnt a new technique skyscrapers from you Mam Thanks a lot

[darcash]

I see. So it wouldn’t work if the squares were not aligned on the cell with an offset/nonalignment since the only intersections would come from cells that were already guaranteed not to have that number

[mingchinglin]

There is a third scenario. The roof cells can both be true. But the rule of elimination is correct.

[sefrzan]

Is it only the roof of the skyscraper that causes elimination of a candidate or can this be done with the base as well?

[deaahimm]

Key thing to remember in finding X-wings or Skyscrapers: 2 "Sides" (2 columns or 2 rows parallel to each other) have to consist of Conjugate Pairs (only 2 Cells in Separate Blocks in a Column or Row contain the Same Number ie in video: b2, h2 and a7, h7) and that on the Third "Side" (in this case, the "Base") the Ends (h2 & h7) just be lined up in a Row or Column. And No, the Base DOESN'T have to be a Conjugate Pair or Matching Pairs. REPEAT: The Ends in the Third Side Doesn't have to be a Conjugate Pair or a Matching pair, they just have to line up. Sounds weird I know, but in a Skyscraper it's on the "Roof" (b2 & a7) where any Eliminations take place. Btw, same rules apply in an X-wing too! The Ends of the Roof (say if was b2 & b7) Doesn't need to be Conjugate Pairs or Matching Pairs (just like in the Base) they just need to Line up. Of course, the difference here is that (as opposed to a Skyscraper) you can also make eliminations in the Base too. Whew! Hope that helps guys! ✌🏼

[MrZ]

I don't understand the logic of the first example. It's clear that if B2 is a 7, then A7 surely cannot be a 7. But it seems there is nothing that says that if B2 is a 2, then A7 cannot be a 5. How do you arrive at the conclusion that if B2 is 2 then A7 must be 7?

[mbillmiller]

Hi. Just found your channel, your stuff is EXCELLENT! Thanks! Just starting sudoku can do easy ones - watched your episode 1-6. Is there a sequence of your videos I should watch ?

[davidgoldsmith]

Looking at the comments below is it therefore true that this only works if the "base" is a matching pair ?

[HonteleJ]

Erm why does H7 needs to be true if H2 is false? 🧐

[francoisepichot]

Hello Thank you so much for your very clear explanations ! Where can I find all your lessons for classic sudoku please ?

[lechj]

@5:28, after elimination two 5s in cells A1and B1, the puzzle looks still unsolvable. What is the next step, please?