Su Doku

Starting on Monday 15^th November 2004, The Times have started publishing a daily Su Doku puzzle.
For example:-

6
	7
8	5

3
	9	5
6

	2
3
9		1

	6	7
9
		1

9		1

2		3

8
		4
7	6

2		4
		6
	3

		6
7	5
		2

	1	7
	4
		8

To solve the puzzle, you have to fill out the whole grid, using the digits 1 to 9. The digits must appear once in each row, once in each column and once in each of the nine 3x3 boxes.

A few basic Techniques

There are a few simple techniques for filling out the obvious squares.
The most basic is to find only a single valid place for a value. Starting with with a cell (a group of 3x3 values)

find a value which isn't already in the cell.
Try this value in each of the blank entries (in that cell) to see if there is only a single one valid space for this value.
If not try again with another value

Try this with the value 3 in the top left cell

This can also be applied to columns

find a value which isn't already in the column.
Try this value in each of the blank entries (in that column) to see if there is only a single one valid space for this value.
If not try again with another value

Try this with the value 6 in the right most column

This can also be applied to rows

find a value which isn't already in the row.
Try this value in each of the blank entries (in that row) to see if there is only a single one valid space for this value.
If not try again with another value

Try this with the value 9 in the 6^th row

As more and more cells get blocked off go back and search for more values in more cells, columns and rows.
Using this technique alone should solve most of the simpler puzzles.

6	1	9
4	7	2
8	5	3

3	7	8
1	9	5
6	2	4

4	2	5
3	8	6
9	7	1

3	6	7
9	2	8
5	4	1

9	4	1
5	6	7
2	8	3

8	5	2
1	3	4
7	6	9

2	9	4
1	8	6
7	3	5

8	3	6
7	5	9
4	1	2

5	1	7
2	4	3
6	9	8

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This page was lasted updated on Wednesday, 17-Nov-2004 02:16:09 PST
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