please empty your brain below
Please don't post your solution here.
But feel free to tell us how you got on.

diamond geezer | Homepage | 19.08.11 - 8:17 a.m. | #

I'm struggling, though I put that down to it being early and my brain hasn't fully woken up yet. I think if I had a pack of cards and could lay out the physical cards I might do better.

Is the fact that in the bottom right hand corner you can only select the Jack of Diamonds a hint or a mistake?

Barry | 19.08.11 - 8:54 a.m. | #

Wow I got game one on my third attempt! More by brute force than intellectual guile I think and I might pass on the hard variant.

Fun though - thanks.

Peter | 19.08.11 - 10:55 a.m. | #

I think I've done it - can we have a submit button that tells you it's right or wrong - bit like online sudoku where you get pink stripes showing your mistakes? Might try the ace one later - too much procrastination, must do some work.

allotmentqueen | 19.08.11 - 11:21 a.m. | #

This reminds me of an incident a few years ago when Sir Michael Atiyah was interviewed by a journalist, who asked him what he thought of the Sudoku craze. Sir Michael replied that he was delighted to see so many people doing mathematics every day, and was taken to task by the journalist because "there is no mathematics in it: you don't add the numbers or anything".

Anyway, I consider this a mathematical puzzle; I even have some fancy words for it (a Graeco-Latin square with two disjoint diagonals and some entries prescribed). But don't let that scare anyone off trying the puzzle!

Thanks, DG: I put a link to it right away.

Peter Cameron | Homepage | 19.08.11 - 11:42 a.m. | #

I remember an occasion in the late 30s, when I was asked for a quotation by a local journalist. I admired the young journalist's persistence, thanked him for his time, and politely arranged for him to be ejected from the club.

Later, I found him at the entrance, gave him a shiny penny and asked him to solve exactly this puzzle. He achieved it; I gave him the quotation he desired.

I found keeping a note of which cards I had used already made this easier.

Alan | 19.08.11 - 11:52 a.m. | #

Had to resort to actual cards to do it, but got it.

Raven | 19.08.11 - 1:15 p.m. | #

I have just done it but had to resort to using actual cards. Though I would like to make it clear I had only been trying it for the last 10 minutes, I hadn't been trying to do it since my first post earlier this morning.

Barry | 19.08.11 - 2:14 p.m. | #

Took me about five to ten minutes. Then I realised my solution was valid for the second puzzle.

Personally, I think the first one is a little harder. A second fixed square locks in the other two corners as being two of four. From there, it's easy to find the middles and then the edges.

Will | 19.08.11 - 7:24 p.m. | #

Just as hard eight years on....

Gordon | 20.08.11 - 9:31 a.m. | #

A pleasant bit of light entertainment. Thanks DG

Veronica 1 | 20.08.11 - 1:53 p.m. | #

Good to see such a blog variation. But am I very alone in not being very good or diligent or interested in completing soduko and similar puzzles? I tend to give up after the first mistake, recognising perhaps that a computer could be used to solve it in 0.000001 sec. I should have tried Go in my youth - it is more like guerilla warfare and tough for computers to play. Sorry to seem miserable, it's not a criticism of your excellent blogs, more a comment on my own dim outlook.

Herb of Romford | 20.08.11 - 2:08 p.m. | #

To Herb of Romford - these were exactly my sentiments when I first learned about Sudoku: indeed, I wrote a computer programme which solved it in some very small fraction of a second, and decided there was no need for me to take any further notice. But then, on a long and boring train journey, I tried one out, and found it a good way of passing the time. Various connections then came to light such as magic squares (which were cutting-edge technology in the Middle Ages: wearing one on your armour kept you safe in battles!), a variant by Robert Connelly with a beautiful symmetric structure and some nice connections with geometry, and so on. Since then I have actually given public lectures about Sudoku in various parts of the world...

Peter Cameron | Homepage | 25.08.11 - 10:40 a.m. | #











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