How To Solve Extreme Sudoku SO Fast You Ignore Difficulty

[00:00:00]You want to hear something crazy?

[00:00:03]A computer solver uses 20 advanced strategies to solve this puzzle. But, I'll show you how to solve it with a simple trick that works time and time again on extreme puzzles.

[00:00:17]And with that, it's solving time. Look where six can go here in block two. With these three sixes, the only place you can put a six is right there. And that is the only solve you're going to get without the amazing Sudoku trick I'm going to show you, greens friend.

[00:00:36]I want to thank Talking Freedish for yet another amazing puzzle.

[00:00:40]It has five-star difficulty on Logic Masters Germany. To solve it better than the computer, I will share something that'll completely change the way you think about Sudoku. But first, the question of the day.

[00:00:53]What is your biggest obstacle to learning something new?

[00:00:57]Is it time, frustration, age? For me, I feel I often don't know the best place to start when I'm trying to learn something new. But what about you?

[00:01:06]Please, please share in the comments.

[00:01:09]Help me grow the internet's best Sudoku community.

[00:01:13]So, the key to solving this puzzle is to notice that you have these twos and threes in the corner.

[00:01:21]This is the key.

[00:01:23]And it has a big effect on where a two or three can go here in block five.

[00:01:30]I'll show you what I'm talking about.

[00:01:32]What can be in block five? It can be one, two, three, or four. You can remove the four because of this four.

[00:01:39]And you can remove the one and four from this cell. All right, I'll remove the colors.

[00:01:45]What you want to ask yourself is you have this one and the two three here in block five. If the one was not there, you had just a two three here, what would happen to where you could solve twos and threes in this puzzle?

[00:02:02]Well, because of the two-three in rows one and nine, you would end up with a two-three naked hidden pair here in column five.

[00:02:12]So, those wouldn't be a two-three because of here. You got a one-four there, you got a seven-eight there.

[00:02:18]Okay, not a big deal until you understand what happens with these values right here. If you put a two right there, well, that puts a three right there. No biggie.

[00:02:30]But, you'd see with these twos and this two, you put a two here in block three, and then with this two-three pair and these twos, you have to put a two right there in block six. Okay, not a big deal until you realize where would the threes go? With these threes, you put a three right here in block nine, and then with these two-threes and the two-three part of this pair, where could a three go here in block six? Couldn't go anywhere.

[00:03:03]It'd want to go right there, but it can't because you already have a two there.

[00:03:06]And then maybe you're thinking, "Okay, Timber Lake, can't just put a two there. What about a three?" Well, if you put a three there, the two goes there, you're going to have a similar situation.

[00:03:16]But, it'll be on this side of the grid.

[00:03:17]With these threes, three right there, and then with those threes and the naked pair of threes, two-three right there, only place to put a three in block four would be right there.

[00:03:32]But, then you notice with the twos, you have these twos and this two, put a two there in block seven, and where could a two go in block four?

[00:03:42]Well, with these two-three right here, it cannot be there, and it cannot be here or here because of these twos.

[00:03:49]It wants to go right there, but it can't because a three's there. So, that's another So, what you know is you cannot just have a two and a three right there. And if you're wondering how this works, the strategy is called a junior X-wing set. In particular, it's set up beautifully by talking Friedish by putting the twos and threes in those rows.

[00:04:14]And what it does is it creates an enormous amount of impact and restriction in these columns right here.

[00:04:26]And what would happen, and I'll show you, is this is where the twos and threes can go in these columns. And if you remove the two and three from these cells, and you put them here, right?

[00:04:45]Well, those cells can't be twos or threes.

[00:04:48]And now if we use the purple to represent all of the threes, and then I'm going to put greens to represent all of the twos, I'll show you that.

[00:05:02]You would know cuz of the three right there, that can't be a two. This can't be a three.

[00:05:07]This can't be a three.

[00:05:10]And this can't be a two. And so, what happens is you have to have three threes in these three columns, right?

[00:05:25]But only two of them can be outside uh along this row and this row. So, the third one's got to be in one of these cells. The same thing happens with the twos, and so they end up fighting over where these cell the twos and threes are going to be right there. And that's is caused by that junior X-wing set. But what it means to you is you want to avoid this situation by not having a two and three right there.

[00:05:56]Instead, you can solve that for a But you're not out of the woods just yet. You need one more advanced strategy to move forward in this puzzle. But first, you can capitalize on the impact you just made. By putting the one right there, you can notice with these ones you can solve for a one in block eight. And then with these nines and this nine, you can solve for a nine right there. And then you might notice and this cell cannot be a one, two, three, four, five, six, seven, or nine.

[00:06:33]This is a naked single eight.

[00:06:35]And it allows you to finish that column with a two-three naked pair.

[00:06:41]And so now, to get that other advanced strategy, you need to look at where the ones can be in this puzzle. At this point, ones can be there, here, here, right here, and these cells right there.

[00:06:59]Okay?

[00:07:01]And then notice put in purple, you look for conjugate pairs. So, this is a conjugate pair in column two, right? A one can either be here, if it's not here, it has to be there. Now, can you match it to another conjugate pair where it shares at least one of the rows? You sure can.

[00:07:18]You can go right here in column eight and notice that they share row one.

[00:07:25]But the tips, the other parts of the conjugate pair, are in different rows of the same three-block band. And so, what that means when you compare it is a one can either be here, if it's not here, based on the conjugate pair, a one has to be right there, which would remove a one from this spot and put a one right there.

[00:07:47]And so what you notice is a one's either got to be there or has to be right here because of the relationship with the conjugate pairs.

[00:07:55]This is called a Sudoku skyscraper and what it means is you can remove a one from any cell that sees these tips and by seeing means shares the block and row. So, these two cells both see these two cells. So, a one can't be there.

[00:08:13]And this cell and this cell, you know, shares the row and the block, so you can remove a one from right there. And so you see color-wise there's only one place left for a one in block six. So, you can solve that for a one.

[00:08:25]And don't take away the colors just yet.

[00:08:28]Since you solved this for a one, you know this cell now is the only place for a one in block three.

[00:08:36]So, ones can't be there anymore.

[00:08:38]And you'll see there's only one place for a one, one colored cell in column one, so this has to be a one right there. And then you can mark these ones in blocks four and one to remind you where the remaining ones are. So, you're making some great progress and now you want to capitalize on the solves you just made. So, look up column one here.

[00:08:59]You might see a one, two, three, five here in column one. If you look at this cell, you'll notice you have a four, six and nine there in the row and a seven in the column. The only thing left for this cell would be a eight.

[00:09:15]If you look at this cell right here, can't be a one, two, three, four, five, seven, eight, cannot be a six either. It's got to be a nine. It's a naked single nine.

[00:09:31]And if you look here, what's remaining in column one you have four, six and a seven. Six and seven right there means that has to be a 4 and this is a 6 7 naked pair. Look at the impact on that because of this 4 now, you can remove the 4 from right there and solve this cell now for a 4.

[00:09:51]And then in block 7, now with these 8s, only place for an 8 is right there.

[00:09:58]And then also in block 7, you'll notice that with these 4s, you can solve for a 4 right here and with this 2, you can solve for a 2 right there. And so continue making progress.

[00:10:16]All right, after doing that 2, look across row 6. So this is called a heavy house that has at least five cells filled out. A 4, 5, 7, 8, 9 need a 1, 2, 3, and a 6. Well, 1, 2, and a 3 all see this cell, right? Cuz they share the column and the block. So that has to be a naked single 6. And so now you just made column 9 a heavy house. 1, 2, 3, 5, and 6 need a 4, 7, 8, and 9.

[00:10:48]And so right here, you have the 4, 8, and 9. So that's got to be a 7.

[00:10:57]And then you're looking for a 4 8 9 to finish here. Well, with the 8 9 right here, that has to be your 4. 9 repeats, so you know the 9's going here and this is going to be your 8 in the column. And then you made more marks here in block 9. So you have a 1, 2, 4, 7, 8 need a 3, 5, 6, and a 9.

[00:11:23]And so you might see with the 6s, this has to be your 6.

[00:11:29]And then with these two 9s, this has to be your nine. And I just need, looks like, three and a five with this five.

[00:11:39]There's your five, and there's your three. You finished block nine. How about block seven now?

[00:11:45]Just need a five, six, and seven here.

[00:11:47]With this six in the row, that's got to be the six. And with this seven, there's your seven, and there's your five. And now with this six, that has to be a seven. And you can see with that amazing trick how this puzzle just coming apart.

[00:12:00]Doesn't even feel like it was a five-star difficulty.

[00:12:04]With these two sevens, this has to be a seven right there, which means that's going to be a two, three.

[00:12:10]And with this two, three, and the one, four, six, eight, nine, you need a five and a seven right there. Can't quite solve that yet, but you can make a little bit more progress by continuing to look across row three here. You have a one, four, six, eight, nine. You need a two, three, five, and a seven. Well, the fives can't be in those columns, so this actually does have to be a hidden single five, which means that's a seven.

[00:12:37]And then the seven can't be here, so it has to be right there. And with this two, there's your three, and that's going to be your two. And now I can disambiguate the three and the two right there. The three and the two right there. And you're solving all of these cells now.

[00:12:53]And you can finish up block two. Just need a three and an eight with this three.

[00:12:58]There's your three, and there is your eight.

[00:13:02]Okay. And then I'm continue on with the solves. You just want to look again where your heavy houses are.

[00:13:08]Look across row four. You just need a three and a nine.

[00:13:14]And with this nine, you know that's got to be the three, and that's going to be your nine. And then with these nines, you can solve for a nine right here in block three.

[00:13:24]Leaves you with just a two, four, and a five. Okay.

[00:13:29]And so, with this four here, two spots for four.

[00:13:34]Two spots for a five there cuz of that five. Can you do better than that? You sure can't.

[00:13:40]All right, you just need a two, four, and an eight here in block six. Well, with these eights, this has to be your eight. That four repeated, you know that's the four that's going to be the two. And now this four tells you this can't be four.

[00:13:55]That's got to be your four right there.

[00:13:58]And now you just need a two and a five here. Well, this two is going to help you solve that for two, displacing that five. These two fives, follow the fives all up and you can solve that cell for a five now.

[00:14:10]Just need a one and a six here.

[00:14:13]Don't quite see the one and six, I'll just make a quick mark and see if you can do it better with another row. You just need a two and a six here.

[00:14:21]With this two, there's your two, there's your six. This will be great the six and the one right there. You know you can displace that one. You solve this cell for one and your last cell is a three.

[00:14:34]Now, challenge yourself to find the extreme shortcut in these next videos.

[00:14:38]Thank you so much for watching.