The New Sudoku Players' Forum

[Gems19810]

Does anyone know of any other websites where I can find the 'killer' sudoku variants? The one killer sudoku in the Times each day is not enough!

[AJ]

yeh!! These new sudoku's are ace the tricky ones are quite hard to get started, but once you get a couple in, they just fall into place

[possum]

I've made 2 false starts on today's killer. I thought it was quite straightforward, starting with the 1,2,3,4,5 in the middle column, but I'm doing something wrong thereafter.

[Spa]

Go with your first thought...the order will work itself out as you go on, and then look at the cells immediately above and below that group of five.

[possum]

Go with your first thought...the order will work itself out as you go on, and then look at the cells immediately above and below that group of five.

yes, I went on to 6,1 for the 7 enclosure in box 2 and 1,7 for the 8 enclosure in box 8. Seemed to be going well for a while afterwards, but then ended up stuck when I came to box 9, when I had 3 and 7 left in column 7, which could not be placed in the 24 enclosure.

I'll have to start again sometime...

[Spa]

If I recall correctly, the four corner boxes tended to get filled in towards the end of completing the puzzle

[possum]

Thanks Spa! I find it quite difficult to 'retrace my steps' when I go wrong, and end up starting again. I may be back for help later.

[tso]

There is a solver here:

http://homepage3.nifty.com/funahashi/game/game676eng.html

I've tested it on two puzzles. It took only a 10 or 15 seconds to solve the one I previously posted before the TIMES started publishing them http://forum.enjoysudoku.com/viewtopic.php?t=995&postdays=0&postorder=asc&start=0, but it took many minutes to solve the "Deadly" one here: http://www.timesonline.co.uk/article/0,,7-1757275_2,00.html

And again -- this solver reported one and only one solution to each puzzle. The puzzle I posted has two other solutions if you ignore the "no duplicate digits in an enclosure" rule that the TIMES forgot to include in their article.

[Enigma]

TSO - thanks for the pointer to the puzzle you'd previously posted. I was on holiday late August, so missed it. More of a stretch than the recent Times ones, mainly because there were far fewer pairs and triples.

The interesting thing for me was that I came across what may be a brand new technique that speeded things up for me - it's probably been discussed somewhere before, but I've not spotted it. It's what I'll call the MUSCLE technique - Malicious Uniqueness Short Cut Logical Extension.

I used it twice when solving it... this is one of the examples:

At one stage I had r9c1 and r9c2 as potential 7s and 9s given the 16 pair. In box 4 5 could go in either r5c2 or r6c2, the latter of which would have left a 7/9 pair in r5c1 and r5c2. I therefore deduced that 5 had to go in r5c2 as otherwise I would be left with 2 potential solutions given the 7s and 9s in rows 5 and 9 and columns 1 and 2 - hence the uniqueness shortcut.

Is this a valid technique ? It's certainly logical given the assertion that each puzzle only has one valid solution... just probably not the intended path to the unique solution.

Paul

[PaulIQ164]

If I've understood what you mean correctly, there's been a couple of threads discussing its use in regular sudoku in the Solving Techniques forum.

[tso]

MUSCLE technique - Malicious Uniqueness Short Cut Logical Extension.

Yes, of course it's valid. There has been disagreement on this issue -- but everyone else is wrong.

See: An Unmentioned Logic Technique .

[Enigma]

Excellent, so we can use muscle as well as brain power.

I suspect that this might crop up a good deal more in killers though by their very nature.

Paul[/quote]