Improve Your Sudoku: How To Solve Harder Puzzles

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4 жыл бұрын

You can try today's puzzle here:
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Hi! We're Simon Anthony and Mark Goodliffe, two of the UK's most enthusiastic puzzle solvers. We have both represented the UK at the World Sudoku Championships and the World Puzzle Championships. We're also "cryptic crossword" aficionados. Mark is the eleven-time winner of The Times championship and Simon is the former record holder for most consecutive correct solutions to The Listener crossword. We hope we can help your puzzle solving while also introducing you to some of the world's best puzzles.
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Пікірлер: 108

@billiardsprofessor 4 жыл бұрын

You often talk about how Mark solves it differently. I'd love to see you two tackle some harder puzzles where you used different techniques to solve it. Or have you done videos like this in the past?

@ragnkja 4 жыл бұрын

The Billiards Professor For a special episode, a comparison between their techniques on one puzzle would be cool.

@kickasyberg7344 4 жыл бұрын

I only solved this because you found the x-wing on the 1's. And I even looked for x-wings. Guess I just stared myself blind with this puzzle PS. One of the things I love the most about your videos is when you go to check the puzzle and there's no mistakes. The way you smile and say "yes" is so adorable and makes me smile every time.

@SvviftDeath 4 жыл бұрын

It took me almost 11hrs to finish this one. I fell asleep during the solve and got something to eat after I woke up. Then I came back and finished the solve. Probably about 26 min of actual solve time. There were a few restricted cells that you overlooked that had simplified pairs. The main one being in Column 8. It had a 26 pair for a long time that was easily resolved. It didn't provide much for me but you might have found a faster method using it that I didn't originally see. I can't spot pointing pairs or xy-wings, swordfish, or empty rectangles like you can yet. I am getting better each day thanks to your videos.

@ragnkja 4 жыл бұрын

SvviftDeath Pointing pairs is the easiest technique of the ones you mention. Whenever you notice that a digit is restricted to one row or column in a box, look at the other boxes that row/column crosses, and see if it helps you restrict that digit in those boxes. This is best done immediately after you notice the first restriction, as it can easily get lost in other notation.

@M4ke4l 4 жыл бұрын

Mark probably used uniqueness, there are at least 2 in this puzzle that breaks it.

@ProfNoetigenfalls 4 жыл бұрын

Beautiful solving technique. I had to do it the hard way by spotting quadruples. I need to get better in spotting x-wings.

@TheJazzNL 4 жыл бұрын

I got stuck on the hidden triple in row 1, sadly had to give up after staring at it for 15 mins with no progress

@georgeaman1938 Жыл бұрын

Thank you Simon and Julie! What a nice puzzle!

@drengskap 2 жыл бұрын

Feeling pretty pleased with my unaided solve time of 31:30. My sudoku really has come on in leaps and bounds thanks to Simon and Mark's tutorials. I owe you guys a Patreon subscription!

@_KingRaz 4 жыл бұрын

What a difficult puzzle. Had me stuck for a long time. Took me ages to see the hidden triple in the top row. Great solve.

@CJVale 4 жыл бұрын

I missed the 234 in the top centre box, once you pointed that out and the X-Wing (which I need to get better at spotting) I was able to get critical mass and solve by unwinding the umpteen pairs I had

@SesakoFTW 4 жыл бұрын

Did it in 40 minutes! This was the first puzzle i could do it, that was posted by you. Thank you for teaching me proper sudoku, ever since I'm having a blast doing them!

@titaniadioxide6133 4 жыл бұрын

By 4 minutes in, you had uniqueness with the 8/9 on row 4, and the 8/9/4 on row 7. That would lead into uniqueness with 5/7 pairs in columns 4 and 5

@jrbr549 3 жыл бұрын

This is the first puzzle that I solved faster. I know he stops to explain. It's a shallow victory but I'll take it. ;)

@NelielSugiura 4 жыл бұрын

Really liking the new thumbnails!

@Soliloquy084 4 жыл бұрын

I did it in 40 mins, my personal best for a puzzle posted here. I used uniqueness to get the 4 in r7c9, and the 1/6 pairs to get the 8 r3c6.

@JeremyButlerquarterthru 4 жыл бұрын

Found a definite uniqueness crack that made it much easier in the 89 combos in c8&9 r4&7, required the 4 to be in c9r7.

@brendabalzan1994 4 жыл бұрын

Holy Moly. After 1 hr, I was stuck, I was about to throw the white towel. I was tired of looking at so many possibilities... I decided to work with 8&9s in boxes 3, 6 and 9... row 7 had to remove 1 of them 8&9s, I saw in one of the columns there was a triple 8&9, therefore 1 of them had to leave, and after that, used the same trick on a smaller scale a few times and solved it! Total of 1hr 15 min and 13s. Now gonna watch the video to see if I did it right/came to the right conclusions in the end. Yay.

@Laserstormelpies 4 жыл бұрын

6:58 this is where i was able to get to on my own (not counting the 89 pair in the bottom center) EDIT: After the trick at 17:53 i was able to do the rest alone Its about time i figure out all these advanced things, so many sudokus bullied me years ago (when i was a kid), now i kinda found interest in it again, seeing how you solve these

@JuanMataCFC 4 жыл бұрын

3:42 i used uniqueness to deduce that the 4 in the bottom-right box must be in R7C9. if it were in R7C7 (the only other position it could be), then the 8s & 9s have a uniqueness issue. this is the first time i used uniqueness, so please correct me if i did anything wrong. thanks! :)

@cameodamaneo 4 жыл бұрын

I love using uniqueness, but it kinda seems like cheating sometimes, as the designer couldn't have used uniqueness while designing it, as they don't know if there's currently one solution at that point, so it's like an unintentional shortcut.

@rabidsamfan 4 жыл бұрын

12 minutes and pleased with it, although I started differently than the video. I saw the 2,3 pair in the bottom right box and the 4,8,9 triple, then lined up the 4th row, saw the 8,9 uniqueness issue and placed the 4 in r7c9. Loved all the triples in this. A fun puzzle!

@stefanovitali2925 Жыл бұрын

Same here, that uniqueness trick was neat! Still needed the x wing on 1 to solve

@Blahblahblahblahize 4 жыл бұрын

Double uniqueness: a) 89 in boxes 6 and 9 which places a 4 in column 9; and b) uniqueness on 57 in boxes 2 and 8 which moves the 57 pair in box 2 to r1c4 and r2c5. Cracks the puzzle v fast

@jrbleau 4 жыл бұрын

Yes, he had those 89s at 3:51.

@splicerdicer8800 4 жыл бұрын

There was actually a single in r5 c8 that had to be a 6 , but it wouldn’t have advanced the puzzle, very nice solve

@Pyromonkey83 4 жыл бұрын

Relatively straightforward 8 minute solve for me. I took a bit of a uniqueness shortcut which probably could have been easily solved elsewhere, but I felt like going for speed today after the hour long glory of yesterdays video. ;) Can't wait to try out some new Sandwich Sudoku puzzles tonight on the app, though! EDIT: Looks like the uniqueness shortcut was a MASSIVE shortcut indeed, skipping the hidden triples and X-Wing entirely. Slightly sad I missed the logic, but glad Simon was there to show me the beauty that I missed with my skip! Great solve as always.

@Pyromonkey83 4 жыл бұрын

@Spider53 That is an option, yes, but personally I used the 89 pair in r4 (box 6) and the 489 triple in row 7 (box 9) to prove that r7c9 must be a 4. This solves a lot of the pairs throughout and gives more in the middle section, plus a couple of hidden singles to finish it off.

@ryokousha 4 жыл бұрын

There is some cute logic involving the 16 pairs that allows solving without the hidden triple and the x-wing. In row 3 the 1s and 6s are restricted to columns 1,2 and 6. Now, if r7c6 is a 1, r7c1 is 6 and r9c2 is 1. These two 1s block two of the possibilities in row 3, so r3c1 is 1. Likewise, if r7c6 is a 6, r9c2 is 6 and r3c1 is 6. So r3c1 must be a 16, which breaks the puzzle. Also r7c9 is a 4 by uniqueness.

@Curundil 4 жыл бұрын

Any chance you can explain the uniqueness spot? I want to get better at spotting those, I'm not quite seeing it.

@Sevicify 4 жыл бұрын

@@Curundil There's an 89 pair in r4c8 & c9. The 4 in question is a part of a 489 triple in r7c7, c8 & c9 with the 4 locked into c7 & c9 due to the 4 in r2c8. Placing the 4 into r7c7 you are left with an 89 pair in c8 & c9, this obviously causes a uniqueness issue with the 89 pair above in r4 where two solutions are possible. As a Sudoku should have only 1 unique solution we can determine the 4 must be in c9 to satisfy this. Another possible usage of uniqueness in this puzzle that I also used is with the 57 pair in r1c4 and r7c4 & c5, depending how you solve the puzzle you may be left with a 157 possibility in r1c5 which can be resolved using the r7 pair to figure out only a 1 can go there. Hope this is helpful.

@04LightningFan 4 жыл бұрын

Hey Simon, at 6:54 after you placed the 9 & 8 in row 9, you could have spotted a finned x-wing in rows 3 and 7 that would have eliminated 6 from R2 C1 and R4 C1 which would have led to some naked singles. Thanks for pointing out the 234 triple in column 6. I think by watching this video something clicked and with practice I will improve at spotting similar patterns.

@sonalita_ 4 жыл бұрын

at 3:51 you can use uniqueness to place a 4 in r7c9 and that gives quite a lot of progress. I ended up witha lot of 16 pairs that fixed the 8 in r3c6 that broke the puzzzle

@Oblivion776 4 жыл бұрын

Got stuck just a little after you did, but I had kept in the back of mind the possibility to use uniqueness on the 489 in the bottom right box. Spent a while looking around for something more elegant but eventually gave up and just took the free 4. Not nearly so adept at spotting those hidden triples, even though I do the NYT puzzle every day.

@neokart2660 Жыл бұрын

I love watching these old videos from when I didn't know about this channel. When I tried this puzzle I didn't use the X-wing at 15:00, instead I realized that r9c2 and r7c6 are the same digit "n", since they are paired with r7c1. So where does "n" go in row 3? There are only 3 places where 1 or 6 can be placed, and two of them see "n" on r9c2 and r7c6 down the columns. So it turns out r3c1= 1 or 6, and so the pencilmark is shifted to r1c1=2, you get all 2's on the board and some 3's, everything goes smoothly after that.

@guapking1000 4 жыл бұрын

the x-wing was the breaker in this puzzle for me

@ib9rt 4 жыл бұрын

Interesting. I tried this first and got stuck, then I watched you solve it and saw you also have a hard time. Later I came back to it and solved it easily and quickly using no technique more difficult than hidden pairs (lots of them) and a few triples. I have found many NYT puzzles much harder.

@Enkil01 4 жыл бұрын

Great solve, way beyond my capabilities, although i did notice when you found the 3, & 4 in top right box, the box below was also then forced into a 3, & 4 double, which gave an instant 2 and a 7. dont know if this would of helped at all. Would be fascinated to see Marks attempt at the same puzzle, as you mentioned you use slightly different techniques. I would find it interesting to compare.

@monzr93 3 жыл бұрын

The 4/8/9 can be resolved by uniqueness in r7, I was very pleased with myself when I figured it out.

@gposchman 4 жыл бұрын

after the 234 discovery, I continued filling the middle squares and the 7's which broke the puzzle for me.

@ThatGuy-dj3qr 4 жыл бұрын

The only thing I did notice at 15:15 was that you could have used uniqueness to save a bit of time. You spotted the two 5-7 cells, but there was an additional 5-7 cell which, by its location precluded a 5 or a 7 in R1 C5. This along with your previous logic means that only a 1 could go in this cell. I think this would have been useful. As always, it's fun watching you solve the puzzle.

@mehrdadmadrakian6109 9 ай бұрын

Very nice

@skavies2351 4 жыл бұрын

I love this channel, but it does get frustrating after a while of me pausing the video, working on it for an hour, getting stuck, hit play, you catch up in usually about 5 minutes...

@killroy42 4 жыл бұрын

I usually think "Oi! Spoilers!" and pause him again ;)

@lawrencekallal6640 4 жыл бұрын

Starting at 11:00, looking at the 36 in RC41, force testing the 6 in the bottom left block 16 pair can eliminate the 6 from that position. Putting the 6 in RC71 eliminates that 6. Putting the 6 in the other position (RC92) and following the forced 6's around, lands a 6 in RC31. So RC41 is a 3. Getting that 3 is enough to crack the puzzle open.

@kennethirving 4 жыл бұрын

One or two uniqueness steps to resolve 4 at r7c9, maybe somewhere else as well. I like your new thumbnails, too, and really appreciate the sudokus!

@glennmelven3414 4 жыл бұрын

When Simon found the 234 triple in box 2 is when I noticed that there was a uniqueness issue with 57s in that box. I had pencil marked 57 in 3 cells and saw because of the 57 pair in R7 that there could not be a 57 in R1 C5. This forced a 6 into R12 C6 which resolved the 16 in R7 C6 which broke the puzzle for me after staring at it for 10 minutes with no progress.

@williampowalski4222 4 жыл бұрын

12 minutes thanks to uniqueness. cheap but effective :D

@BlueCyann 4 жыл бұрын

Massively screwed it up somewhere last night, but only about 30 minutes this morning with a fresh start. Pretty happy! Edit: Such different logic! I eliminated the 1 from r1c1 with a finned x-wing (eliminated a 6 from r2c1 the same way though I don't remember it helping), I used uniqueness on the 89s along the right, and I spotted the hidden single 6 in box 6 really early. I *think* the rest was basic Sudoko, including reducing r1c1 to just the 2. At some point I had the 7s along the right, which gave me a second 16 in column 2, and that provided a break in the top rows which led to the whole thing falling into place. Meanwhile Simon takes the puzzle in almost the opposite direction with hidden triples I still struggle to see. Very very cool.

@jeffmarquis4612 3 жыл бұрын

The very last cell you filled in (6) was a naked single before you did any x wings. I think missing that is the essential difference in your and Mark's solving styles. Patterns vs weak cells.

@rilian226 4 жыл бұрын

I noticed that you could have done Snyder on 4''s in the top left block from the beginning. 3 4s intersected there leaving only 2 spots a 4 could go in. I am not sure that it would have helped much...

@theojenkins533 4 жыл бұрын

loving the new thumbnails👍

@TheJazzNL 4 жыл бұрын

I like them too, the old ones used to annoy me for they spoiled the puzzle a bit when opening the link in the description on mobile devices

@FrankThuerigen 4 жыл бұрын

as in this case i normally start looking for hidden triples and quadruples much earlier than you - but this also makes me much slower an admittedly is error prone. Also by diving into this early I tend to miss info I could have gotten from what I already have at that time. Like, I missed the 5s in row 1,2... on the other hand, I had a 4 and 7 solve before you that way. But - great video as always... thanks.

@timsullivan4566 4 жыл бұрын

The key to this one was looking for how the 2.3.4 in the top centre 3x3 restricted their placement in column 6. But what, in general, is the indication to start look for that? p.s. - is there a way to contribute without having a credit card?

@DiacriticalOne 4 жыл бұрын

At 5:49 there are two moves that would have sped it up a lot. Col 8 has to be 34(72)(89)6(72)(89). Then uniqueness solves the 4 in col 9. That one set kind of breaks the whole thing open.

@SirGeeSantos 4 жыл бұрын

44 min. ;) getting better.

@rabidsamfan 4 жыл бұрын

I didn't get there that way, but I noticed in the video that when Simon places the 5,7 pair in r1c4 that he could have used uniqueness to solve r1c5 right away.

@brianking992 4 жыл бұрын

I did it without the x-wing. At that point rows 3 and 9 in column two were a 1&6 pair so the only remaining one in row 1 was in column 5.

@howardtoob Жыл бұрын

Wouldn't it be interesting to see how many different ways there can be in order to solve this puzzle? Any ideas?

@ahmedzhanaymuradov9548 3 жыл бұрын

when i had a picture around 15 minutes i've colored all 6s posibilities and looked at 7th box, so whereever is 6 can go in box 7 then 6 never goes to r4c1 and after i put there 3 in r4c1 everything became clear

@Wouter10123 4 жыл бұрын

11:50 How the hell does one spot something like that?

@Kingcob7 4 жыл бұрын

uhhh I "bifurcated" one of the 89s but didn't find out I was wrong until only a few numbers were left, then I gave up and watched how you solved it :D

@Czeckie 4 жыл бұрын

I've solved it by using uniqueness twice

@cameodamaneo 4 жыл бұрын

What were they? I only found one.

@marie513 4 жыл бұрын

@@cameodamaneo 89 & 57 .... or at least those were the ones for me. Made the solving pretty quick

@rickroll9086 4 жыл бұрын

Can do it pretty straight forward w just the 57 in column 4 and 5.

@stronggreenflame 4 жыл бұрын

I'm surprised he missed the naked single in R5C8 for so long. he's usually really good at spotting weak cells. for me it was the 16 pair on the bottom row that broke the puzzle for me.

@r0bw00d 3 жыл бұрын

I've worked this one three times and, despite the simplicity of it all, I've arrived at three different uncompletable solutions. I don't know what's wrong and I don't care; I'm never going to tackle this one ever again.

@richardfarrer5616 4 жыл бұрын

Proud of myself that I spotted the empty rectangle on 6s in the top middle block marrying up with the 1,6 pairs in row 7. A shame that all that did was exclude 6 in R2C1 but when I looked at it further I got a chain (not sure what the official name is) showing that 3 was impossible there too. Therefore that cell had to be an 8. I feel there must have been a simpler way to exclude the 3 from that cell than I found though.

@francescobertozzi8809 4 жыл бұрын

I used the same technique. If you looked carefully r2c3 was a 5 or a 6, therefore, the empty rectangle allows you to Place a 3 in r4c1

@anirose9874 4 жыл бұрын

did it in 41 minutes!

@bobmerritt7442 4 жыл бұрын

I put it in the dailysudoku.com Draw/Play, filled in the unique singles, and it graded "too herd." I hit sweep, getting all the possibles, spotted an X wing and then reduced the 57 unique rectangles in squares 2 and 8. Got her done in 8:49. Uniqueness is a beautiful end-around -- maybe I like it because I found that general technique without help. There are likely more ways to leverage uniqueness than have been found.

@justanotherdude655 4 жыл бұрын

The 6 you filled in at the last number, i found out way before, because of the rich numbers crossig h^this spot

@nicholasiverson9784 4 жыл бұрын

I think his solving method is one of those situations where a creator can't accurately gauge the difficulty of a puzzle, I'm guessing at 3:53 when you eliminate the 4 in row 7, to create a unique puzzle they forced a 4 into column 9 next to it - looking up at row 4 the 8/9 pair interacts with it there. Otherwise it would force an 8 and 9 into column 7 at the top there and have two solutions where you swap the 8s and 9s from columns 8 and 9.

@Xarlus 4 жыл бұрын

I did exactly that and about an hour later hat to do the uniqueness technique again. It was really hard that way around. The 234 triple plus x wing was way more straight ahead

@ragnkja 4 жыл бұрын

I may be a bit strange, because I noticed the _inverse_ of the 234 (a 1689 quadruple) instead.

@topilinkala1594 2 жыл бұрын

From 3:52 I started to wonder how come Simon do not notice immediately that there is 89 pair on row 4 and in r7c8 and a 489 triplet in r7c9 which means that r7c9 must be a 4 or otherwise there's uniqueness problem. When I did this I noticed it immediately and it cracked the whole thing open. Simon actually never even noticed the 89 pair on column 7. If he'd had he would have noticed the 72 pair on the same column and that in box 6 the center therefore must be 6. That's the way I continued after the uniqueness solving.

@birdiesify 5 ай бұрын

I solved this by checking columns and rows missing 5 numbers they repeatedly threw up couples and used uniqueness which C the C seems not to like .

@bfish89ryuhayabusa 4 жыл бұрын

Actually, in Mark's video on pencil marks, I think he did comment that you restrict your notation to 2 whereas he will do 3. However, he uses the center pencil mark spot for Snyder, and I prefer your use of the corners to distinguish between Snyder and other marks.

@bfish89ryuhayabusa 4 жыл бұрын

Though, I commented on that video that I have noticed that you consistently use red to denote positives, which is precisely counter to how that color is generally used. Of course, such things only matter as far as being consistent, but still, I do find it quite perplexing.

@xitvono 4 жыл бұрын

I tend to do like Simon and use corner marks for where a number can go in a box, while using center for candidates for a cell. If I get stuck I tend to fully notate a puzzle, then remove the corner marks and use corner marks for bowman's bingo. Also, I don't see a reason to restrict myself to only 2 squares for snyder notation.

@rabidsamfan 4 жыл бұрын

It always seems to me that Mark seldom needs to mark in two ways because he's so fast at spotting restricted cells. I need two ways, though, so I'm very happy with this software.

@brianrichter8255 4 жыл бұрын

I use Simon’s system, corner = Snyder and center = cell candidates. I heard a variation on Snyder notation where you are allowed to mark 3 possible cells in a box but only if they’re in the same row, which I try occasionally if I get stuck. If I’m more desperate and need Bowman’s Bingo, I just enter my guess directly, since the web app makes it easy enough to backtrack. Sometimes I’ll undo a correct guess and try the wrong one, because I want to know the reasoning.

@grenvillephillips6998 4 жыл бұрын

A very good puzzle but there are too many tricks to be useful at my level. As I learn to spot individual tricks I find it better if they arrive one at a time.

@alexandertharpe8738 Жыл бұрын

I thought I was getting decent at sudoku... and then I watched this video

@Edmocci 5 ай бұрын

The “controls” only gives a list of instructions? I could have sworn there used to be actual controls.

@eireannsg 4 жыл бұрын

14:16 at this point you have missed something important. R1C5 is not a 5 or 7. 5,7 Unique rectangles and it can not be 2,3,4,6,8,9....remains 1

@Coyotek4 4 жыл бұрын

25:17 ... I wonder if using uniqueness is fair for a puzzle like this. Twice, I bifurcated in the (known) wrong direction to convince myself that a certain square was not a 4. All that winding and unwinding takes time.

@PhotoYo 3 жыл бұрын

My ocd dislikes the coloured boxes

@joelowthianYT 3 жыл бұрын

14:08, you've identified that row 1, column 4 is either a 5 or a 7. How?

@kaschmir3 11 ай бұрын

Because those are the only places the can go in that column. Look for the restrictions of 6 and 7 in box 6 and row 9

@michaelbaker9347 4 жыл бұрын

anyone else use uniqueness to get the 4 in Column 9, Row 7? there were 4 pairs of 89 in columns 8 and 9, row 4 and row 7

@sHillChannel 4 жыл бұрын

I like how you say you never put 3 cells in a box, when you did it on 346 (and it was still 3 4s while you said you never do it).

@kevinkk111 4 жыл бұрын

There is a small difference in it since he doesn't put 3 in a box unless they are guaranteed to be of a combination like 236 in any of the 3 cells

@tomekduresov706 4 жыл бұрын

9:30 not that hard, but very enjoyable..

@the.mr.beacher 7 ай бұрын

Talks about not adopting 3x pencil marks at same time there's 3x pencil marks in boxes 4 & 9 😂

@twalton 4 жыл бұрын

Please do a tree themed sudoku to support #teamtrees :)

@NMalteC 4 жыл бұрын

With respect this is a not so hard puzzle, one case of uniqueness solved a critical 4 for me (8:41, very obvious in the right side of the grid), 12 minutes. That's nowhere near the speed you masters can achieve though, by it's certainly a result of all the videos you have put out.