This POWERFUL Strategy Solves Hard Sudoku When Others Fail

[@SmartHobbies]

Get your own personalized solving video here 👉👉buymeacoffee.com/timberlakeb/commissions Timestamps 0:00 Intro 00:25 It’s Solving Time 01:12 Puzzle Story 01:31 Crosshatching and Snyder Notation 04:06 Critical Solve 06:10 Pointing Pair 07:30 Filling Out BVCs 10:20 BONUS Strategy 12:26 Get Your Personalized Video 13:07 Setting Up Powerful Strategy 15:52 Powerful Strategy Revealed 17:42 Following The Snyder 18:05 Sweeping The Blocks

[@laszloliptak611]

Nice puzzle. Solved it in 24:12 using basically the same techniques.

[@SmartHobbies]

Awesome Laszlo. Congrats on solving it and thank you for the comment.

[@JohnRandomness105]

If I'm stuck, I fill out the grid. At least I have an alternate use for the cornermarks then. I'll see what happens with this puzzle. Later, the puzzle is finally finished. I filled out the grid, as I expected. After a while being stuck, I found a short chain that placed a digit. But it still did next to nothing. I finally bifurcated on a bivalue cell and slowly finished it. 1:25 I went back and checked: the green cell was the last digit I placed. 9:45 At this stage in the grid, I'd placed one more digit: 3 in the lower-left corner. I'd also centermarked the grid. I noticed that 6 (out of 68) in R2C1 forced 9 in both R7C1 and R8C1. So I placed 8 in R2C1 and 5 in R2C9. I would have saved time had I placed the final 5 in block 2. This really didn't do much; I was still stuck. 11:30 Surprisingly, your W-wing corresponded exactly to my short chain (described above).

[@SmartHobbies]

There are many times I end up filling out the whole grid as well. 👍🏻

[@andrewatherton316]

After the first run through doing Naked Singles and Synder notation, it's always useful to repeat that process again and again until no more pencil marks or figures are placed. Placing the 4's reduced number of places for 3 in block 4 and solving the 3 in block 7.

[@SmartHobbies]

I agree. How do you like to run through the Snyder, chronologically or just as you see them?

[@andrewatherton316]

@@SmartHobbies Numerically! Ascending! (Old school!) LOL. At the same time looking for claiming pairs. But this means I might miss some of the symmetry that could help to crack more difficult puzzles.

[@ke9tv]

Yeah. At around 07:30 I started singing '3 in the corner!'

[@hansvandenhof]

Thanks for a wonderful puzzle. For my solution I used the XY-chain r2c1, r3c3 and r3c7 so I didn't need the W-wing.

[@SmartHobbies]

Very nice find, Hans. Thank you for sharing your experience. How long have you been watching the channel?

[@francoisepichot181]

Thank you so much Timberlake ! It is in fact easier to solve the puzzles (on paper) thanks to your methodic way of writing snyder notations and especially trying to keep only bivalue cells on the grid so it is less confusing than filling all the numbers possible. I know some theory for advanced rules so you gave me a very good way of getting better at solving puzzles 😊 I notice that it is also (as far as I am concerned) often a lack of concentration, I must work at that too 😉. Again thank you very much for your great work ! We keep in touch ☺

[@SmartHobbies]

I love that you reached out to me. This puzzle was a joy to analyze. Please keep in touch to let me know how your Sudoku journey is going.

[@eugenetswong]

Thanks. I forgot that there is a difference between XY Chains and XY Wing.

[@SmartHobbies]

You are welcome. I am glad I could help.

[@BradJames878]

I'm disappointed in my 54:44 time to do this puzzle, not including the time I spent to peek at the video. I figured out this puzzle would take having a lot of cells filled in with all possible candidates, so I did that. I couldn't find where the w wing would be, so I clicked through the video just long enough to see which cells were involved. I had already looked at those cells, but as I recalled how a w wing works, I'd have to use the strong link between the 9 and 4 in block 9, and that wouldn't help any. Maybe there are different ways of doing the w wing (not counting Delta Variant), I don't know. As for the XY chain, I had to do it twice, following two different paths, to solve for 8 in block 8. And that solved the rest of the puzzle for me.

[@SmartHobbies]

Nice, Brad. There were a couple of different XY-Chains that work at that point.

[@pawovado]

I found also the elimination of the 6 in cell R2C1 and the I examine cell R1C3 and fill in a 7 and became a contradiction in row1 of 8's, I don't saw your wonderfull wing

[@SmartHobbies]

Nice job spotting that contradiction. Have you ever participated in the Sudoku Grand Prix before?

[@pawovado]

@@SmartHobbies No, but I play for fun and not for stress. No competition

[@SmartHobbies]

@@pawovado Awesome. Do you prefer solving from an app or with paper and pencil?

[@sharmilisharmili472]

Used an AIC (type 2 )twice to solve.

[@SmartHobbies]

Wow. Nice. Do you remember which cells you needed it on?

[@sharmilisharmili472]

​​@@SmartHobbies First route of an AIC type 2 ( Starts with a strong link from some candidate say "x" in the START cell and ends up with a strong link but on diff candidate say "y" in the END cell AND both cells (start/end) being in the same house , then the end candidate can be deleted frm start cell and the beginning candidate frm end cell) START cell R2C1= 68 END Cell R2C7=69 Starts frm 8 to 6 as a strong link within the cell R2C1 and final landing is at the cell R2C7=69 following the route R2C1(68)--- R7C1(69) --- R9C3(678) --- R9C9(46)--- R8C7(49)--- R2C7(69)( Strong link frm 9to6 within the cell R2C7) Thus 6 eliminated frm R2C1=68 turning it to single 8. This leads to some placement of digits R2C9=5 R1C4 =5. Also R9C1= 3 due to vertical 39 pair in box 4. Again second route of an AIV type2 Start cell R2C4= 49 (strong link frm 4 to 9 within this cell) R3C4=89 R9C4=48 R9C9=46 R7C9=69 R7C1=69 R3C1=67 R3C9=78 R1C9=78 R1C3=17 R2C3=16 R2C7=69( END CELL, Strong link frm 6 to 9 within this cell) Thus 9 gets eliminated R2C4=49 changing it to single 4.

[@sharmilisharmili472]

​@@SmartHobbies First route of an AIC type 2 {start cell - R2C1( Strong link frm 8 to 6 within this cell) AND End Cell - R2C7( strong link frm 9 to 6 within this cell) The cells follow the route mentioned below. R2C1 (68) R7C1(69) R9C3(678) R9C9(46) R8C7(49) R2C7(69) END CELL The digit 6 gets deleted frm R2C1=68 turning it to single 8 Thus R2C1=8 R2C9=5 R1C4=5 we already had R9C1= 3 at that point of time in the video. Again we can apply an AIC type 2 . Although it is very lengthy route but anyway diff frm ur solve. Start cell R2C4(49) ( strong link from 4 to 9 within the cell) End cell R2C7(69) ( strong link frm 6 to 9 within this cell) It goes as... R2C4(49) R3C4(89) R9C4(48) R9C9(46) R7C9(69) R7C1(69) R3C1(67) R3C9(78) R1C9(78) R1C3(17) R2C3(16) R2C7(69) END CELL The digit 9 gets deleted frm R2C4(49) modifying it to single 4. Rest all can be solved . Btw, this is the second time I'm replying, the first time it all got wiped out.

[@SmartHobbies]

@@sharmilisharmili472 That must have been frustrating. Thank you for sharing your AIC Type 2s. Very nice find for this puzzle. 🧩

[@bigfootmm]

At 5:51 that seven placed in row 6, column 9 is not logical inasmuch an in row 5, column 8 there is a seven-nine pair.

[@bigfootmm]

Nevermind, nof I see a four in that square with the seven. Wasn't there the first time I looked! Ha.

[@SmartHobbies]

No worries. I appreciate your comment.

[@JamesKiraly-oz1nc]

Why did you choose row 8 column 6 as the green cell? Is there a reason or just arbitrary? i have watched numerous solves by you but you never indicate why you choose the cell you solve for.

[@SmartHobbies]

Great question. I will now reveal what is “behind the curtain.” I do solve these puzzles before making the video. I find a cell or cells of interest that can usually only be solved by finding the hardest or intended strategy. The idea is to help you see how much closer we are to solving a particular cell of interest with each step along the way. Hope that helps.

[@AnonimityAssured]

I got through this pretty quickly, but only by using a virtual chain to break through the crunch point (1 = row 1 column 7): 17, 35, 54, 97, 72, 47, 82, 76, 15, 41, 11, 92, 75, 95, 91, 62, 52, 89, 44, 64, 58, 56, 94 (a 4 here fairly quickly leads to a conflict, owing to the pairs in column 8)*, 16, 34, 38, 67, 46, 66, 43, 63, 48, 27, 79, 97, 99, 71, 23, 13, 28, 18, 24, 14, 29, 39, 19, 31, 21, 83, 93, 86, 96, 81, 69. * R9C4 = 4 → R1C6 = 4 → R2C8 = 4 → R1C8 = 1 → R9C3 = 6 → R7C9 = conflict. Now to watch and be enlightened. While I'm here, though, here's a quick couple of variations. First, an enjoyable speed run with lots of hidden singles: 000 200 000 060 031 000 045 000 200 070 060 001 802 000 705 100 050 020 007 000 840 000 610 050 000 007 000 000200000060031000045000200070060001802000705100050020007000840000610050000007000 HoDoKu rating: Easy 508. Andrew Stuart rating: Gentle/Easy Grade 69. Second, a grid that puts up a bit of a fight: 000 200 000 060 031 000 045 000 200 070 080 001 402 000 507 100 090 060 007 000 840 000 610 090 000 007 000 000200000060031000045000200070080001402000507100090060007000840000610090000007000 HoDoKu rating: Hard 1138. Andrew Stuart rating: Tough Grade 121.

[@SmartHobbies]

Thank you Julian. I like that you solved this puzzle. Excited to check out the variations as well. Do you like having the puzzle difficulty ratings showing in the video?

[@AnonimityAssured]

@@SmartHobbies I do. It's a good idea. As it happens, HoDoKu gave me a higher rating for this puzzle, which helped me to remember that I had disabled Uniqueness strategies. There are a couple of harder variations on hold, by the way.

[@SmartHobbies]

@@AnonimityAssured I can’t wait to see those as well.

[@eugenetswong]

@@SmartHobbies I appreciate seeing the ratings.

[@SmartHobbies]

@@eugenetswong I am glad to hear that. I also like to know how hard a puzzle is before I start it. I also thought viewers could try for their own personal records of highest rated puzzle solved