Best XY-Wing Video Ever! Sudoku Advanced Tutorial 16

In Best XY-Wing Video Ever! Sudoku Advanced Tutorial 16
by Smart Hobbies, I show you how to find and solve Sudoku XY-Wings. In this Sudoku Advanced Tutorial, I define Sudoku XY-Wings also known as Bent Triples or Y-Wings. I also show you how to find and solve cells involved in Sudoku XY-Wings by using examples from my previous videos. Below is the list of examples with puzzle and video links:

Example 1 Classic Sudoku by Florian Wortmann

Example 2 Classic Sudoku by Tyrgannus

Example 3 Classic Sudoku by R. Kumaresan

This video is part of my Sudoku Advanced Tutorials playlist on my YouTube channel, Smart Hobbies. The goal of this series is to share the joy of solving Sudoku puzzles with you.
#learn #sudoku #youareawesome

Strategies demonstrated in this video:

XY-Wings

Check out Smart Hobbies page on Harold Nolte’s Sudoku Primer website here:

Contact me here:
CTC Fan Server (Discord): Timberlake#1905

I used the software program CTC App for this solving video.

Let me know what you think and how you did in the comments below. Thank you so much for watching.

Timberlake
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[SmartHobbies]

Time Stamp
00:22 XY-Wing Example 1 (Shared Row)
04:22 XY-Wing Example 2 (Shared Column)
06:56 XY-Wing Example 3 (3 Blocks)

[Thfeyhvfdetyhbvcd]

I didn’t understand xy wings.

I struggled a little with your first example.

Your second example led to my AH HAH moment.

I found the xy wing in your third example in four seconds!

I was ecstatic!

WELL DONE!
WELL DONE!!!

I then saw ANOTHER way to look at it! Search for a triple.
34 14 13 is a 134 triple. Maybe the wrong term, but you see what I mean.

Once you find a triple, see if it’s positioned as an xy wing.

Again
56 35 36
It’s a 356 triple
AND it’s got a pivot with two pinchers

And finally
27 29 79
It’s a 279 triple and I spotted it almost immediately!

I was blind, but now I see!

Thanks for your excellent explanations!

[Thfeyhvfdetyhbvcd]

Update! I was really stuck on a recent “impossible” LA Times sudoku; then I watched this video. I returned to that sudoku and quickly found an xy wing. From that point the entire puzzle was a breeze!

Thanks again. I’ve subscribed!

[helenhill]

This just messes with my head! I never make notes in my Suduko puzzles, as I find it too confusing (I’m autistic). I’ve developed my own ways of solving them and memorise the options in cells. I like to do the hard level of Killer Suduko and the best I’ve achieved is solving it in less than 3 minutes, beating 99% of people, though I’ve only managed that once. My average is about 5 minutes. I cannot do the expert level though, as I don’t make notes. 🤦‍♀️

[anaayoung]

I will coment in the first 2 videos because I couldn't do alone, but the last one I could solve by myself 😂 unbelivable

Thanks for this video!

[Whoknows]

Finally I understand this. Thank you so much ❤

[hungnguyenviet]

I use it when I’m stuck for ideas, and it’s very good

[brucewayne]

I think I've been seeing these without realizing it. But I do find colouring (for me) a good technique to eliminate possibles.

[ckoh]

Begin with the instant takeaways :
The three sets of 5&9 given on r1, c7 & c9, all outside of B3 => [59] tcp (true conjugate pairs) on c8B3 between rows 2&3.
8 on c8@(68), by virtue of 8s given in Boxes 3&9, on r4, all off c8, allowing 7 given @(52) to squeeze in at (48), thereby leaving [13] tcp on r5B3 bet cols 7&9.
Now right away we have 6 on r4@(42), thus leaving 1 in B4@(62) and also at same time leaving 135 triplet on r4B5.
1&8 uncovered on r6 outside of B5 => 279 left on r6 B5, with [79] tcp bet cols4&5, leaving 2@(66) => 2&4 on c5B2 and 9 on c5B8 [CIY= check it yourself]
So Middle Row Block is quite well broken up except for r5B5.
Let’s move the war theater to Top Block.
Again right away we have 6 on c4@(24) and on r1B3, plus cell(26)=[18], by point count.
Other bivalued cells are :
(12)=[34], (23)=[13],
(15)=[14], (37)=[24].

Now here’s a nittygritty for the trained eye :
1@(11) would result in 3@(23)&4@(15) ==> cell(12) = ZERO!
So 1 is eliminated from (11) and the only other place else on r1 for 1 is at (15)!!, by v of 1 given in B3 and uncovered on c2@(62).
The technical description to what happened is 134 form an XYZ System with Xat(12), Y at (14), Zat (32), whereby for 1 at (11) to look at 1 in Y and Z would lead to a disaster. ( it’s a skill to detect the system and pick the right candidate to eliminate)
Indeed there’s alternative way to go abt it : 1@(11) would lead to [67] tcp on r1B3, by v of 6&7 uncovered on c2 and in B2, all off r1, resulting in 3 on r1@(12)==> cell(23) = ZERO!
So 1 uncovered @(15) => [24] tcp on c5B2 and 8@(26) ==> [89] tcp on c5B8 bet rows 8&9, by v of 8&9 given on r7, and uncovered on cols 4&6, all three off B8! Plus 1 in B8 on r8 bet cols 4&6.
Also 8 uncovered at (26) => together with 8 given on r1, both off c1, 8 on c1B7 => [89] tcp c2B1 bet rows 2&3.(indeed 8@(26) => 8 on r3@(32) => 9@(22).
Now we are in the presence of an intriguing situations :
[24] tcp uncovered on c5B2 bet rows 2&3, and [24] uncovered cp on r3 at (35)&(37) ==> by Uniqueness constraint, 2&4 cannot be at cell (27) but 3&7.(right now this is a weak info)

Here’s a really nittygritty observation :
3 at (92) would lead to 4@(12) and 2 on r9@(99).
Uncovering 2&4 on row 1 and on col 9. ==>!! [24] tcp on c7B3 bet rows 2&3 !!, a NO - NO to Uniqueness rule.
Therefore the only other place for 3 on row 9 is at (98)!!
AND this the break we are looking for!
So 3@(98) and in tandem with 3 uncovered @(59), both off c7 => 3 on c7@(27), as anticipated plus 3 on r1@(12) => [36] tcp on c3B7.
3@(12) => 1@(32) => leaving [47] tcp on c1BI and[18] tcp on c1B7 => [45] tcp on c2B7, by v of 4&5 given on r9 outside of B7, leaving 2 in B7@(92).
Now in hot pursuit 3 uncovered @(37) => 7 on c7@(87), by v of the three 7s given on rows 357, all off c7!, followed by 2 on c7@(37)(see it coming?), leaving 4 on c7@(77) (indeed 3 @(98)=> 4@(77), by pt-ct.) and 4 in B3 @(18), by the 4 given on c9 squeezing in, whereby leaving [67] tcp on c9B3 and leaving [16] tcp on c8B9 and finally [29] tcp in B9 on c9!
One more step to go :
4 uncovered @(77) => 5 in B8 on r8 forming tcp with 1, and leaving 3 in B8@(75) => [13] tcp on r4B5 bet cols 4&6 with 5@(45).

Eureka!
The tcps will eventually all be broken up by the appropriate danglers.
I leave them to good hands. Have fun!!

[fubaralakbar]

This can also be done when the pincers don't have a common candidate. For example, if II6 was 3/7 in the first example (although it obviously couldn't be in this scenario), we would know that since the 3 and the 4 can't both be true, either the 7 or the 1 is true...so we would look for any eliminations caused by both of those candidates.

[JohnRandomness]

I found a Y-wing (134 in blocks 1 and 2) fairly early in the first puzzle, which gave me a few digits. I had considerable work following, and I can't remember most. Backtracking to see what I did, I remember skipping a little logic to establish a set of 13 cells as remote pairs, but it worked. I chained to show that either R8C1 or R7C7 was 4, which finally cracked the puzzle.
The second puzzle: I bypassed any Y-wing, or maybe I did it in disguise. In the endgame, I was trying to extend a sequence of 48 cells, when I wound up showing that a certain 48 cell had to be 4 regardless of the other 48 cells. That cracked everything. I'm not sure whether part of that step was a W-wing, a 38 pair mediating two 48 cells.

I just began the third puzzle, and already found a finned X-wing in 2s. (Perhaps the more surprising thing is that it actually removed a couple candidates.) A little later, a finned X-wing in 6s. (After penciling 7s) The 6s finned X-wing turned out useless, as the 7s gave me a 27 pair anyway. (After filling block 1 with three pairs) The 6s finned X-wing turned into a full X-wing. (How things oscillate on me.)

(After a break for dinner) Another finned X-wing in 8s, a Sashimi type. It would have been a skyscraper if column 6 didn't have three places for 8.
(After more time) I found a Y-wing (257 in rows 2 and 4). It was there ever since a finned swordfish in 7s, although I didn't see it until just now. An earlier 235 triple in row 4 did more damage to that cell, so the Y-wing was useless.
(An instant later, after a scan of the grid) I just found another Y-wing (367, rows 5 and 9) that might crack the puzzle. We'll see. (A few minutes later) And the puzzle's done!

0:50 The first puzzle. That Y-wing is the one I found fairly early in the puzzle. I needed a lot more to finish the puzzle, though.
5:20 I backtracked to the point where the Y-wing is visible in my grid. I missed it, but I'd already placed the 9 long before the Y-wing became visible. Block 1's pointing pair in 3s eliminates the same 3s as the Y-wing.
7:30 That Y-wing was visible in my grid for the longest time, and I never saw it. It was visible during the finned swordfish in 7s -- I used three of the four cells, the ones with 7s. That Y-wing would have done at least the same damage to the puzzle, and partially resolved the finned swordfish. It was visible when I found the different Y-wing near the end of the puzzle. (Once I found that, it didn't matter.) I suspect that spotting that Y-wing would have made solving this easier.

Thanks for the video.

[windchwang]

Got stuck at 7:01, bcz after I do all synder notations, still can’t figure out where to fill the 6 and 9 in block1, so I can’t limit R2C8 to 2 and 9. Then I re-checked and saw the X wing of 6 that could help rule out 6 in R2C8, the rest was all similar to the video😂