Learning to play Sudoku is difficult without an illustration, but with a
good imagination, you can get a general idea. If you want to see how a Sudoku
grid looks like, just click on the link at the end of this article and store
that image before we proceed.
The first thing you see when you look at the puzzle is a large square, the
grid, containing 81 squares. This is like a chessboard with nine squares on top
and nine squares on the side, intersecting to form eighty-one squares. This
grid has nine columns going from left to right and nine rows going from top to
bottom.
For every three squares, four thick lines – two drawn from top to bottom and
two drawn from left to right – form a mini-grid of nine squares each. Each
mini-grid is a three by three square so the grid, the large square, has nine
mini-grids.
An easy Sudoku puzzle may have twenty-nine numbers printed in different
squares and several mini-grids. Using these numbers as starting clues, your
goal is to fill up the remaining squares with numbers.
How do you start?
Picture yourself looking at a Sudoku puzzle for the first time. You see the
grid, the mini-grids, and the numbers.
You can start anywhere, but I prefer to take the upper left mini-grid first.
What I do next is move from the left upper mini-grid to the right lowest
mini-grid, filling up each box in the mini-grid with the possible numbers that
can go into each empty square. You will find out what these numbers are from
what you already see printed on each row, column, and mini-grid.
By a process of elimination, you fill in each square, from top-left to
bottom-right, going from the top row to the bottom row in each mini-grid.
Your big problem is the size of the square as printed in the newspaper. How
do I solve this? I duplicate the puzzle on my PDA, enlarge the image, and work
at it.
It takes around ten minutes to fill up all the boxes, and the process of
elimination begins.
These are the clues to watch for:
Look at each mini-grid. Study
each empty square (without given numbers) filled with the numbers that can
go in that square. If a number appears only once in that mini-grid, this
means that that number should be in that square.
When you identify a number
that belongs in a square by this process of elimination, erase that same
number from the other squares in the mini-grid and from squares where it
appears on the same row and column.
Do this for all the nine
mini-grids.
Next, look at each row and
column and do the same process of elimination. If there is a number that
appears only on that row and on that column, then that number belongs in
that square.
Erase that number from the
other squares in the mini-grid. There is no need for you to erase it from
other columns or rows, since it appeared only once.
Do this for all the nine row
and nine columns.
After doing all these meticulously (it usually takes me twenty minutes or
less to do it), you are left with two or three squares in each mini-grid with
two or three numbers that can possibly fit in.