Hello and welcome to cracking a cryptic now today I’m gonna have a look at a puzzle from the puzzler sodoku magazine which is one I often get this comes from their hard section now it’s not all that hard a section normally I’d say the puzzles range between fiendish in the times and a little harder.
So they’re not that difficult normally and that’s kind of my issue with this puzzle is I had a go at it and I did solve it and it took me a heck of a long time taught me well over eight minutes and then looking back it seems fairly clear that it’s fairly straightforward.
So do feel free to have a look at it see how you would do with this and then what I’m gonna do is explain how you can make progress actually very fast but I’m not entirely sure how you meant to see the possible progress that you can make.
So here we go I mean I hope you’ve had a look at it I’m gonna start explaining now and then i’ll pause for a bit at the bit that I think is difficult so to start with I think that there are a couple of numbers that are f airly straightforward to enter.
If you happen to be looking at eight there’s only two given eights but they’re positioned very usefully for this box up here so the eights that we have this eight rules out those three cells this eight rules out those three cells so that’s the only cell.
The box for an eight and similarly there’s another very simple number down in the bottom where we have some nines in what we’re calling a chute across the bottom.
We have a nine in the bottom row a nine in the next row up so the nine in the row above that can’t be in this box or this box so it’s in one of these two cells and this nine tells us which one now that’s straightforward.
Now what is the next number that you’re gonna put in this is the question for me and I didn’t find it easy to find the next number I think I probably spent most of the eight and a half minutes that I took looking for the next number.
So have a look around and see what number you think goes in this grid next and then i’ll tell you which number you can find and how it makes it very straightforward.
So pause it if you want I’m gonna go straight on now and the thing to spot next first of all you use this one and this one again there’s only two ones in the grid so that one rules out these two cells and this one rules out these three cells that means that there’s a one either here or here and that’s important because that means that there’s a one in this box those three cells are ruled out as well.
As those two because of this one so there’s a one either there or there.
Now why is that helpful and I mean it’s not immediately helpful it doesn’t help with ones across in the rest of the boxes at the top what it does help with is that that suddenly makes this cell here a naked single now what I mean by that is on its own there is only one number that can now go in this cell before.
We decided where the ones went in this box this could have been a one or a two we’ve got five seven three four in the row six nine in the column and eight in the box that leaves one or two but now because these ones are known to be in column seven this must be a two.
I think that after that sing single discovery that one discovery this puzzle starts to fall apart fairly quickly we can now place it two down here to nine one seven I don’t exactly remember.
Where I went from here but to you know i what I did find is one side got that too everything else was very straightforward but how do you spot what isn’t quite a naked single it’s only a naked single once you know that one is not in that cell and that’s quite.
A hard thing to just come up with I just I do want to prove that it was fairly straightforward after this but I’m not quite not quite sure where I went next – yes twos are very useful so again on a similar principle – must be neither here or here and therefore this ones are – and that that fixes the seven in this top left box.
We know that three and four must be in the middle column of that box and that fixes one an A and I mean you’re off from this point it is fairly straight forward now seven here for instance and seven here if it will you know it won’t finish itself you still have to finish it off but most of the donkey work is done just on that one so that one sell that one identification made this puzzle for me a hard possibly took.
It over eight minutes when had I been able to see that within a few seconds the puzzle would have been done in three I don’t know how to go about kind of coming up with a way of spotting those I think you know one of what I had to do was do some of our our Snyder notation where I know Possible’s and eventually.
I spotted that these ones meant that those ones were in place and then I had to switch away from Snyder type thinking to cell type thinking and look at that cell which had so many different numbers pointing at it that it became very useful I’m not sure.
I’m giving you a recommendation for a technique except that you do have to switch between narrowing down where things go in boxes and looking at individual cells and if you could do that right in this puzzle you sailed through it in no time and that’s probably the mark of a truly good Sudoku solver so well done if you did spot this all done.
If you spotted it while I was talking but also well done if you had a look at the puzzle on your own and spotted it fairly quickly because that that was a really key breakthrough in the puzzle thanks for watching just a quick – and I hope to see you again on cracking.