### Friday Puzzles #55

Mission accomplished! Weekly numbering is now completely in order. Modulo the missing #7 and #17 that is. Still, there were a couple of weeks where I made bonus puzzles so I think that just about balances out the equation. I must add that I revisited the double-toroidal sudoku, but I have to say that with its current grid I lost a bit of interest.

Anyhow, a sudoku variant this week which I think I’m right in claiming has only ever been pulled off by yours truly – although please correct me if I’m wrong. In case you missed the original post the idea with 10’s sudoku is normal sudoku rules, except that every time a pair of adjacent cells had digits summing to 10, they are marked. Where there are no markings between adjacent cells, the conclusion is then that the relevant digits cannot sum to 10.

Prior to that post, I can’t find an example where 10’s sudoku had no such marked occurrences between pairs of digits, but it turns out with a bit of work that it’s perfectly possible. I’m sure a computer-y type would easily be able to write a program to churn out more of these without working up any sort of a sweat, but that’s not the way I roll. There’s plenty of potential with this variant to churn out some really fiendish challenges; this example is fairly plain sailing, but perhaps with a couple of surprises along the way. Enjoy!

**UPDATE:** My apologies to those who had a go at an earlier version of this puzzle, which had two solutions, and my thanks to Jack who pointed this apparently obvious blooper I managed to completely miss! My reputation for errors seems to be growing, but stick with me anyway – at the very least you won’t be bored!

All puzzles © Tom Collyer 2009-10

## 3 comments by 1 or more people

## Jack

Er, I’m not getting a unique solution. Specifically, I see two ways of sorting out the placement of the 1’s and 9’s in some of the corner blocks.

05 Jun 2010, 00:25

Blah – you’d have thought I’d have at least been able to get a sudoku right – but no, you’re exactly right. I totally need to test solve these :\

Anyhow, I’ll take this down and get this fixed in the morning.

Thanks for your feedback :)

05 Jun 2010, 00:53

Sod the morning – I clearly couldn’t let something like this get in the way of something as trivial as sleep. This updated version is good!

05 Jun 2010, 02:08

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