What to Do When the One-Thru-Nines Doesn’t Work in your Sudoku Puzzle!

This was recorded during Sudoku Week 2020 on October 6th. Transcript below.

Hey, everybody. We’re back answering questions that you have sent in. And today I am going to, or this session here, I’m going to answer a question. At least I’m gonna answer half of the question that Metallicaddict#1 asked. He says “what do you do when I’ve gone through the one-thru-nines, like 10 times, and I still have only doubles. How do you decide what number to try to continue the puzzle?”

Well then this next person, Modest, replies to that, he says, I feel like I’m at the same spot or I’m utterly blind. There’s a lot to unpack in this one and I’m going to go through it.

The second half of the question, really about how do you decide what number to try to continue with the puzzle, I am actually going to answer that in the next one, because I have two other people who have essentially made the same comment and I’m going to deal with that separately.

So his comment right now, his question, what do you do when you’ve gone through the one-thru-nines, like 10 times and you still have only doubles. Now this is an interesting thing it’s hard, of course, it’s really hard to answer because I don’t see that particular puzzle. It would be varied from one puzzle to the next, although maybe he’s actually running into the same problem multiple times.

I’m gonna try to unpack this a little bit and give you some hints and tips here about what to do. So first of all, if you really have only doubles, what does that mean? That would mean that every space on the board that’s empty has two possibilities and only two possibilities. So if I take him at his word and he’s not exaggerating here if he has doubles everywhere that would mean every space on the board has only two possibilities.

Actually that particular situation is a problem, okay? It’s actually unsolvable. You actually cannot solve the situation where you have doubles everywhere. There’s no logical solution. You actually do have to flip a coin in order to figure that out. I call that particular situation a Doubles Dead End. There is no solution. Out in the Sudoku verse, the other name for it is the bivalue universal grave or graveyard. And basically what that means bivalue means two possibilities in each space. And then universal that it’s every space on the board, and then graveyard means that it’s basically a dead end. That is a problem. If you really do have bivalue or doubles, as I say all over the board.

Now, how did you get into that situation? Well one possibility is that what ended up happening is that you actually made a mistake. That’s one of the possibilities somewhere, you made a mistake and you jumped to some conclusion and you wound up in this situation. That’s one possibility. Another possibility is that the puzzle is bad. So wherever you got the puzzle from the puzzle maker could have done something and not actually tested the puzzle to see if it could be solved by logic. And you wind up in a situation where it’s just bad. You know, when you’ve wound up in this dead end situation, the puzzle is bad.

Now I would actually say that that situation is probably fairly rare, okay? I don’t know that it happens that often, but it could actually happen.

So, however, what if I don’t take him at his word? So he says he’s got doubles. He says only doubles, okay. What that may mean that he has mostly doubles and he has some spaces that are that are not doubles. Some spaces can have three or more possibilities. Well, in that situation, there’s probably some logical solution and it may be, there’s this technique that I call it the doubles dead end solution. Other places call it the BUG or Bivalue Universal Grave plus one. And that actually is a possible solution to the puzzle.

If you have very few of those spaces, you have doubles everywhere except for a few spaces that can be like three numbers. That’s a possible solution to the puzzle. It will require you learning a new technique. The core of your question though, is you’re stuck and you don’t know what to do next. And to tell you exactly what to do for that particular puzzle or for any particular puzzle, would be impossible without seeing the puzzle. And I would have to address that right there.

However, what you really need to do is you need to get more skills under your belt. That’s really the core issue here. And one of the skills that, I mean, well, I mean, for example, in this particular case, I was talking about it is one of the skills that you might need is learning the bivalue universal graveyard plus one, or what I call the doubles dead end.

That’s one technique, doubles dead end solution. But when you’re in this situation and you’re stuck, you really got to think there’s something else I need to learn. And that’s really, really important.

So I want to show you this book here. This is not exactly anything to do with Sudoku. “Five Steps to Expert”, except for the fact that we’d love to become experts at Sudoku. Now, this book was recommended to me by a friend. And it’s an interesting thing. So this guy, I’m not going to do the book justice, I’m just going to briefly talk about some very interesting aspects of the five steps that he talks about to becoming an expert.

Step one is that you are a beginner whenever you start anything new, like you’re starting to solve Sudoku, you are a beginner. You move on in that, do you become what he calls Capable. You then move on and you have some level of Competence. Then as you progress, you get Proficient and then you become Expert. Okay, so beginner, capable, competent, proficient, and expert are the five steps.

The interesting thing is, and again, I’m not going to do the whole book justice by this one thing, is that a lot of times when we’re at the Beginner to Capable stages, when we’re at those early stages, we don’t really know what we don’t know. And we think that we know it all. And actually, if I look back on my own journey, I remember when I first started solving Sudoku and even well into you know, a couple of years into actually being Sudoku professor, I thought I knew it all. I mean, it was pretty arrogant of me at the time.

But I thought, what else is there to learn? And then guess what, here we are 11 or 12 years later here I am. And I’m still learning new things. I’m still learning, as matter of fact, tomorrow, I’ve got a call with another one of our top club member contributors, and we’re going to discuss a new technique he and one of our other club members have come up with and are fleshing out. And we’re going to see what we can do to work that in this new technique on what we call quad combos and using the logic of how these quad combos can be spread around the board and to solve puzzles. I’m still learning. And the thing about it is that when you’re newer in this whole thing, when you’re at the Beginner, the Capable, even into the Competent, you don’t realize that there’s so much more to learn.

And so you look at a puzzle and you think “I’ve done everything I can do” what you probably, you have done everything you could do, but you’re not realizing that there is more that you can learn.

And so I want to encourage you together and learn more, you know, watch these videos. I’m giving you a lot of stuff this week. This is Sudoku Week! We’re celebrating, and I’m giving you all this stuff you can learn from these videos. You can sign up for my free lessons. You can purchase my lessons. You can join the Sudoku Professor’s Insiders Club. And all of these things would allow you to learn in a…The great thing about my lessons, I mean, you can learn around the internet, but I have a systematic approach and it’s very structured.

And you build as you learn. So you’re not watching one video where you’re talking about something fairly straightforward. And then the next video you’re talking about something extremely complex. You’re building on that. And for those of you who are members of Sudoku Professor, and you have learned, if you would like to comment and attest to that, I would appreciate that.

So now let’s see here. Marianne says… Hey, Marianne, how are you doing? “How do you decide on another technique and what to try first, you know, either or three corners and stuff like that.” That’s a great question. Let me think here, this kind of leads into what we’re talking about here, because Metallicaddict#1, one thing is he’s stuck.

What do you try next? So you do know more techniques. What do you try? Part of that, like, for example part of that is what is the puzzle giving you. Then you talked about the either-or technique, which is a form of coloring. Well, as we talk about in the either-or lessons we’re looking for a particular pattern of where the numbers are. You remember that trapezoidal pattern that we talk about there. Do your pencil marks show you that? If they show you that, go for it. With the three corners are you seeing those doubles, the bivalue cells as we call them the pairs of numbers, are you seeing a lot of those that you can start to try to put together to form the three corners, which other people call an X, Y wing or an X, Y, Z wing?

So one of the things is your techniques are being driven by what you’re seeing on the puzzle. And the other thing that we’re doing, what you’re talking about, Marianne, are our Master’s Prep level courses. That’s sort of a mezzanine level in between Bachelor’s and Master’s, we have this Master’s Prep. Some of those techniques are in there.

So you’ve exhausted what you feel like are all the Bachelors techniques, you want to move on, you want to know what to do next, you should look for those things. I would look for them in order. I would glance around the board. Does the either-or pattern catch your eye, if not, do you see things, the patterns for three corners? We move on into the Master’s level, how about some double doubles that would lead to a potential deadlock? Okay. Do you see any of those around there? That’s what I look for next. And then we start looking for other things like four corners, our cloaked four corners is like an X wing as well.

Anyway, that’s the process is that you are looking for, you’re learning new techniques, and then you’re learning how to apply those techniques as you go on. So Metallica and Marianne just keep practicing. That’s another thing that you have to do is you have to practice. Practice, practice, practice, okay. The more you practice, you know, I would say that don’t give up on puzzles and don’t guess, we’re going to get more into that in the next video. But if you can avoid that, then what you’re going to end up doing is you’re going to learn more when you force yourself to find the logical reason to solve the puzzle.

Alright well, that pretty much wraps it up here for this video, but I’m going to continue on with Metallicaddict’s question about how do you decide what number to try to continue with the puzzle. I’m going to do that in the next video. Thanks for joining and watching us live.



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Robert Barker