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Qetuth
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Re: Tournaments
Reply #357 - Nov 28th, 2007 at 12:29am
In the hope of more times being posted: My tactics for S19T3. Sorry for the long and double post anyone who doesn't care. One point, I can never stand using ?marks. I do a lot of mining and unmining as working, and am somewhat used to either resolving or remembering how to put things back how they were when done.
To start, wait for a board wih what looks like fairly full side columns, or at least a large number or two in them. Guess the first couple of numbers out of these to get you started, then solve as much as you can of those (hopefully most of the top 5th). I then quickly look down the rows for ones with enough to reveal mines and put those in (I recognise pretty much all of these from genius), then look over the columns, testing any I think theres a remote chance of giving more info.
I do this by, for example, running down a column, marking as if everytihng was squashed to the top. If I get to the bottom and there are 3 blanks left, every block of mines has 3 removed from its start (the top in this case), so if you had a 4, the bottom mine would be left.
Example of the way I do this:
With 1243 in width 15 (or height 15 in genius:
Mark from left, gives 2 spare cells left at the end, so remove 2 from every block:
M_MM_MMMM_MMM__
X_XX_XXMM_XXM__ <- Xs are ones removed
________MM___M__ <- Remaining mines.
With many 15 width boards now I know these, remembering them by: 1234 means two from the 4 and one from the 3. But for other sizes I still figure out by quickly going one way to mark, then back the other way to unmark.
Mines already there can help this process: eg if you have a block get to the square before a mine, then that mine must at least be part of the block or one before it, so skip the square after the old mine and continue: This basically gives you a one mine advantage for the second half of the column. But not for the first half, so be careful.
Other things I particularly look for, as they seem to occur a lot in this board, is cases like a column starting with 113 and the 5th square is a mine, so the 4th can't be. Similarly a column starting 34 and mines in the third, ninth and tenth, so the second block of mines must be part of the 4 but it can't stretch back far enough. These type of things seem to occur a LOT in this tourney compared to genius.
Once I've done as much as I can by basic methods like that, I look for an "influential" cell, and look at (often by marking mines all over the place), what I know if the first square is a mine, and what I know if the first square isn't. Logically, anything common to the two scenarios is certain. In theory, and square on the board could have this process applied and tell you new information, but most squares in sparse sections don't tell you you anything new for both being a mine and being safe, just one or the other, and in some logically hard dense sections the two scenarios will tell you exactly opposite information.
Mines likely to be influential include:
--A first mine in the unsolved section of a row or column starting with a large number: If it starts with a 6, and its a mine, then the first 6 are mines. So if you discover by the surrounding rows that it not being a mine mean the third cell is a mine, then the third through to the sixth are all mines either way. These cells are particularly powerful in corners.
--Any mine in a row or column which is only one cell too big: Eg, if the first cell is not a mine, then the rest is certain, so see what happens if the first cell is a mine. Then try that at the other end. Or a square in the middle of the row which intersects an important column.
--A row or column with only one block remaining, particularly a 1 or a 2. Anywhere you place that mine clears a lot of cells, so look at what those cleared cells do, particularly all at once. You can often eliminate much of one of these rows.
That's about all I can think of. As far as guessing, in a bigger board I think it's safer to guess something with a high probability of being okay (opposite to a smaller board where you can play enough games that the time advantage of a bad guess is too much to pass up). However, it's pointless guessing something that wont help you significantly, because then you'll just end up making another guess right after. So don't guess something that you can't see leading to more info in several directions.
Hope this helps someone. Good Luck.
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