fell into the 'this is easy' trap and made a mistake... finally finished
great medium puzzle
*phew* went to the archives and finished an 'expert'. Think that's my first
Nearly done with March,then... :\
is anyone talking to me
This one started slow... I usually get more quick 'must go there' spots on n easy, but as soon as I started scanning rows and columns with just a few items left, I found enough to fill in the rest of the board.
What I like about the easy ones is, you don't have to use the greens.
Darn, I guess I'll have to use the greens.
Woo, I've got a flag.
Now I can conquer the world
Nice flag. Beertje, did you do Expert level without any mistakes?
I've gotten through medium and a reacent "easy" hard with no greens. With mediums, when I do use greens, I usually find the spot that I missed that I didn't need greens for.
Difficulty score 19. Cross hatching is the only technique needed. Definitely can be done without green.
Even with greens I'm getting stuck!
Hang in there, you'll get it.
Thanks, just made a little progress.
Virtually everyone knows the cross hatch technique (see the Wikipedia article on Sudoku if you are not familiar with the name cross hatch).
But it is possible that some haven't figured out how easy it is to use the cross hatch technique.
Consider that the puzzle is partitioned into 9 3x3 blocks, and there are 3 columns (stacks) of blocks and 3 rows (chutes) of blocks.
Just consider one of the stacks of 3x3 blocks. It is composed of 3 columns of 9 cells requiring all 9 digits in each column.
If the digit 3 (for example) is in 2 of the 3 columns, you automatically know that the column without a 3 has only 3 cells where the digit 3 can go.
You know it because the digit 3 can only appear once in each of the 3x3 blocks in the stack. So the missing 3 is in the intersection of the only block and row without a 3.
The rest is simple. There may a digit in one of the 3 candidate cells and there may be a 3 in one of the rows intersecting the block so only one candidate cell remains.
Darn it! A mistake. I seem to make mistakes when I use the greens.
Is it considered "fair," when you don't understand the logic, to set a checkpoint, make a guess, and see if it works out?
For the expert puzzles that may be the only way to solve some of them.
Oops, I made a typo a couple of comments back. In a stack of 3x3 blocks with the digit 3 appearing in 2 of the 3 columns in the stack, you know the digit 3 can only appear once in each block so the intersection of the only COLUMN and block in the stack without a 3 is where the missing 3 must be.
When you discover you've made a mistake, is there any technique for unwinding it down to the offending move?
Not if you set it in a checkpoint. If the mistake is set in a checkpoint the only thing to do is start over. That's why I only set checkpoints if I'm absolutely sure I'm correct.
this is too addictive
I'm running through the archives and keep going "Just one more..". I'd better stop or I get an overdose
The archives are addictive. I used to start with Babble but now I start with sudoku to build up my confidence then get to babble if I get to it.
mwah mwah mwah!
haste makes waste. now I gotta start over... I'm with Douglas.... mwah mwah mwah!!!!
Whee! . .a point ...
done and done. probably doesn't need greens, but it is oooooooh so easy if they are used right from the start (I tend to on every puzzle, it helps when you're dispraxic & dislexic)
That was quick :)
btw, is it just me or is this place a bit quieter than it used to be?
Good answer :P
There is one problem with sudoku: it's more interesting than homeworks!