Thursday, July 2, 2009

Glossary of Terms

For clarity I thought I'd define what the terms used in this site mean.

A SQUARE is single cell in the puzzle which contains a number.

A BLOCK is 9 x 9 grid of squares, there are 9 blocks in total in the standard Sudoku puzzle. When we talk about BLOCK 7 we mean the BLOCK in the botom left corner. BLOCKS are arranged as follows:

1 2 3
4 5 6
7 8 9

A COLUMN is a line of 9 squares running from top to bottom.

A ROW is a line of 9 squares running from left to right.

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Sunday, June 21, 2009

Advanced Sudoku Solving Techniques

If you get stuck using the basic methods, then there are other tools at our disposal. The first is to take a look at a square that has no candidates in it. Starting with the number 1 see if it already occurs in either the column, the row or as a candidate pair. If it occurs elsewhere in the block as a candidate pair then it cannot occur in the square that we are looking at. Also if the number occurs as a candidate pair anywhere in the column or row then it cannot be in the square, but the candidate pair must be aligned with the target square. Work your way through all nine numbers and if there is only one candidate left then it is safe to assume that it is the answer.

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Thursday, June 18, 2009

Solve Sudoku the easy way

If the thought of filling a puzzle with a large number of possible candidates for each square fills you with dread, then this method will suit you. It relies on only penciling in candidates when there are only two possible candidates left for a block. See this page for an example of easy way to solve sudoku puzzles.

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Wednesday, June 17, 2009

Play Sudoku online free

You can now play Sudoku online for free. Choose from a variety of levels from very easy to fiendish.

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Tuesday, June 9, 2009

Sudoku solving techniques

As in the previous post two candidate pairs in two adjacent boxes but this time with only one column or row aligning indicates that the number exisits in the comon column or row. Take a look at this page Solve Sudoku 4 and notice the candidate pairs for the number 1 in boxes 2 and 3, notice that they both have a candidate in row 3 meaning that in box 1 the number 1 can not occur in row 3.

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More Sudoku solving techniques

If you have found two candidate pairs in two boxes for the same number and they are aligned parallel to each other, then it is certain that the two rows or columns contain those numbers. The only thing is you won't know the exact location of either of the numbers.

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Sunday, June 7, 2009

Solve Sudoku

One additional tool to help solve sudoku puzzles is to look at a square that has no candidates or perhaps just one. Take a square with no candidates in it and have a look for numbers that can NOT be considered a candidate. Use cross hatching and candidate pairs within a box. If you have found candidate pairs in a box other than the square you are looking, then it is impossible for that number to exist in that suare. By a process of elimination you may be able to find the only number that could exist in that square.

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