Learn To Solve Diabolical/Extreme Sudoku - The XYZ Wing

We take a look at last Friday's Diabolical Sudoku from The Daily Telegraph. Nothing too hard until an XYZ wing appears - and this is a good chance to explain the difference between this and a Y-Wing!

[@drakenskag]

Just ran into the xyz-wing in my latest puzzle. Thank God for this channel. I've been picking up sudoku (again) and I had never really delved too deeply into strategy before. Your channel has been helping me understand some truly difficult stuff for my brain to understand simply from a written explanation.

[@user-yz8wr8vb7f]

I suspect that these "bent triples" were in some of my previous diabolicals, so I will definitely be looking for them in the future. It is much more elegant than my forcing chain method, which I use as a last resort.

[@LinXiaoChaun]

I prefer the (equivalent, arguably simpler) reasoning: an 8 in R2C3 is unacceptable, because assuming 8 in R2C3 leads to an illegal outcome, namely forcing a 3 in R3C2 and a 4 in R8C3, thereby eliminating all candidates (348) for R3C3. This reasoning would also apply to R1C3, if that cell were not already fixed. Just a different way of thinking about the XYZ wing.

[@saultheman3665]

what are you talking about

[@pearlinperil9985]

Make sense

[@nathanvanduiven5728]

Love the bent triples, this is going to revolutionise completing my sudoku books.

[@goster4070]

Thank you for another lesson!

[@rabidsamfan]

Nice explanation!

[@finbarrhayes5878]

Great stuff

[@samuelking4723]

I know this is very late and unlikely to get a reply but at 4:26 how did you resolve that 4? I can’t see why you could rule it out of the top left corner of the grid, or the bottom two corners of its box.

[@Onika4203]

Same I'm also wondering

[@i_am_loki_]

​@@Onika4203C6 has 2 and 9

[@Has39.bfpo43]

Row 1, C1,5&6 must contain either 2,4 or 9. Well column 6 already has a 2 and a 9 in it, leaving only 4.

[@samuelking4723]

@@Has39.bfpo43 Oh my god how did I not see that, thank you!

[@LittleAngel775]

Very helpful

[@dmitry-ie3vd4ll2z]

This sudoku can be solved using only basic and tough strategies.

[@gasperix]

4:22 why is 4 not possible in C1R1?

[@hamzahussain7794]

Because R1C7 and R1C9 can only contain 7 or 8. The remaining squares can contain 2,4,9. Now in R1C6 there can only be a 4 because of the 2 and 9 in the rest of column

[@mrabadisa]

may i ask you please. How we can have the App you are using?

[@LittleAngel775]

What application is that?

[@robertritchie325]

What is the name of the program you are using?

[@davidh.4944]

This one is Duncan's Sudoku Solver. They used several interfaces in older videos like this, before they created their own. Speaking of which, I wish they'd take some time to port these old puzzles to it, or even better, give us a configurable grid.

[@iLuvHardStyle]

This puzzle has way more numbers to begin with than what i just starter solving.. im stuck 😅

[@solfeinberg437]

Where's the puzzle?

[@ivandolinic5675]

At 4:27, how did you know that that particular cell ina first row has to be no 4?

[@zacharysherry2910]

The two and nine are already in the sixth column, lower down. (We were looking for 2,4 or 9 in the first row).

[@ivandolinic5675]

@@zacharysherry2910 but 4 could go into the first cell (top left) as well at that moment, no?

[@zacharysherry2910]

@@ivandolinic5675 no, because since 2 and 9 cannot go there then 4 is the only option without doubling Numbers in column six

[@ivandolinic5675]

@@zacharysherry2910 ok i just got it now.. another question, how did you end looking for specific numbers such as 2 4 and 9?

[@zacharysherry2910]

​@@ivandolinic5675because those are the only three numbers left to find in the first row, since 7+8 are already going to be taking up the squares in the 7th and 9th column (in whichever order).

[@miikonori2653]

Why must it be a 4 at 4:26 ?

[@KL13923j]

2,4,9 for possibility , and the column already have 2,9 so must be 4

[@shubhamkr0]

this is not extreme... I'd call it hard.

[@miikonori2653]

Why must it be a 4 at 4:26

[@jessicaramirez3974]

Because it couldn’t be a 2 or 9