by **PaulIQ164** » Wed Sep 07, 2005 4:53 pm

Right, I'll get through as many things as I can think of:

First, this should really be in the Times forum, but never mind.

Now, Killer sudokus. A simple trick to remember is that, since every row, column and box in a sudoku puzzle must contain 1 to 9, every row, column and box must logically add up to 45 (1+2+3+4+5+6+7+8+9). So, if you look at the Killer in today's times2, and look at the middle row,you'll see it consists of a bar of four cells adding up to 10, another adding up to 30, and one extra cell (the one in the very centre). Since the entire row must total 45, and the two bars of four together total 40, you know that the central cell must be a 5.

A controversial topic that you mention is the possibility of repeated numbers in an L-shaped enclosure. The Times have never specifically stated that this can't happen, though their stated rules sort of implied it. However, tso, who knows a great many things about stuff like this, assures us that it's an oversight on The Times' part, and it is in fact a rule that the no dotted enclosure can hold the same number twice. So, as an example, look at the top-middle box in today's puzzle (Box 2). There's a 2-cell enclosure that totals 3, so it must contain the 1 and the 2 in some order. Now look at the L-shape enclosure totalling 6 that just pokes its head into this box. The only way to make 6 is with 1+2+3. But you already have a 1 and a 2 in the top-middle box, so the part of the L that's in this box must be the 3.

One more example (yes, OK, now I'm just doing this for my own benefit). The very middle column has to total 45. You'ce got a big huge bar in the middle 7 cells that totals 35, so the cells at the top and bottom must add up to 10. The one at the top, as mentioned, must be a 1 or a 2. So the one at the bottom must be a 9 or an 8. But notice that it and the cell to the left of it have to add up to 16. If it were an 8, you'd need 8+8. And you can't have two 8s next to each other. So it must be a 9. That means next to it must be a 7, and you can place the 1 and the 2 in the 3-enclosure at the top.

Most importantly, once you have a few numbers in, don't forget to use the normal sudoku tehniques too!