How To Solve Sudoku Empty Rectangles - Sudoku Advanced Tutorial #2

In How To Solve Sudoku Empty Rectangles - Sudoku Advanced Tutorial #2 by Smart Hobbies, I show you how to find and solve Sudoku empty rectangles. The focus is on demonstrating when to look for these strategies in the puzzle solving process and then how to correctly apply them. I solve all the puzzles logically without guessing.

Puzzle 1 Links:

Strategies featured in this video:

Empty Rectangle
W-Wing
XY-Wing
Unique Rectangle
Finned X-Wing

This video is part of my Sudoku series and 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.

To get more information about the shapes an Empty Rectangle can take in the starting block, I recommend this video by Sudoku Swami:

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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[thomaswilke]

This is like a “let’s go on an adventure and look for an empty rectangle together and we might find one sooner of later” kind of video

[zanzaboonda]

The repetition in this was really great. Thank you.

[NigelPepper-zj]

Great Video. Please can someone explain how at 18:11 you were able to immediately put in the 8 and the 2 in the bottom blocks - I can see that it's possibly to do with Unique Rectangle but still cannot understand how an 8 was placed immediately followed by the 2.

[JohnRandomness]

1:00 Starting the puzzle myself. (Much later) I'm not sure how far I got, but I'm stuck now.
7:50 There is an empty rectangle in 4s in the picture. Unfortunately, it's useless (like the X-wing you found in 3s previously).
8:15 You described it right after I penned this comment.
10:10 I never found that empty rectangle in 8s. For once, I had a very good reason: I never penciled an 8 into that cell (R4C8) in the first place. The 8-pair in block 4 prevented that. (In your grid, it removes three 8s from row 4. Also, if you look over there, you'll see a 146 triple in column 2, that places a 9.)
11:00 Again, you mentioned it right after I penned that comment.
13:30 You win this one. I never found that empty rectangle in 6s. It seems to place a digit. I'm going back to see what I can make of it. (Considerably later) I got some mileage from placing the 4. Then got stuck again. After a long time of trying various things (coloring 68s, for example) I finally hit on a *short* chain that began with the 26 in R7C5. Both possibilities ruled out 2 from R5C4, and the puzzle finally yielded.

15:30 I've not yet learned the W-wing. Early in the puzzle, I thought I was processing an XYZ-wing, but it turns out not. I still have to work on that.
15:50 Without the W-wing, I didn't have the Y-wing, but I still placed that 4 -- it was the only position in row 1.
16:45 I'd placed 9 in R7C8. Other than that, your grid is identical to mine where I got stuck for a long time.
17:15 "I've just about solved this puzzle." If I'd said that here, it would have been famous last words.
18:00 You used a variant of uniqueness that I didn't get, at the potential 56 deadly pattern. I admit that I didn't see the pattern in my solve. But is it necessary to place both off-digits (2 and 8) for uniqueness? The 2 should finish the puzzle, if it's valid.

19:00 I see a finned swordfish in 1s that eliminates a 1 in R6C5. Then you get an X-wing in 1s and a swordfish in 1s in the other orientation. (They do the same thing, eliminate another 1, the fin of the first swordfish.)

The END Thanks for the video. It appears that I need exercise in spotting empty rectangles as well as other positions. It's possible marking up the grid too much causes visual noise that keeps me from finding the patterns.

[charmingpea]

Great Explanations. For me I look at ERs the other way around, and I didn't really get it until I did. For example the first elimination (by ER) at 10:00 I would have looked at the pair in c3 and then followed across into the other boxes. If r1c3 is true that forces r2c8. Alternatively r4c3 is true, and in both cases the target r4c8 cannot be true. I think the reason this works better in my mind is because the pair in the column is an easier starting point to visualise the two alternatives.
Anyway, I've been enjoying a few of your videos, so well done and keep it up!

[jrbr]

@ 15:20 it's just a locked pair 6, 8 in box one forcing 4 into r2c1.

[ArvindGupta-jxwg]

Can such problems be solved in paper pencil format without the help of the computer? Your views will be appreciated.

[andyleung]

Just come across this puzzle and don't quite understand why R7C4 has to be 2 and R8C9 has to be 8 ? Thanks