Overview

Sudoku is a logic based puzzle consisting of nine 3x3 squares. A Sudoku puzzle will be presented to you, but only partially completed. Using the starting squares as a guide, you use logic to divine the numbers that must be placed in the other cells of the grid. This logic relies on the fact that - in Sudoku - any number (between 1 to 9) must appear in each row, column, or sub-square only once. So, if a row already contains the numbers 1-8, the remaining cell "must" contain a 9. The same is true for columns and sub-squares; combined these form the basic 'logic' required to solve Sudoku.

Solving Sudoku

There are a lot of appliable techniques to solve Sudoku's, including some very mathematical formula based solutions, but below is a quick breakdown of the most common method. However, it is all based over the "One Rule":

Complete the Sudoku (filling ALL blank cells) so that each row, column and subsquare (3x3 box) contain the numbers 1 to 9.

Any "solving" method will always have to follow the "One Rule". The only difference between each "method" is the efficiency and complexity of each; how quickly it will allow you to solve a Sudoku versus how difficult the "method" is to execute. With that in mind, here is the "standard" method.

1. Systematically approach every cell and fill each with every possible option (represented by a smaller number in the square; see example).
2. Now, look for "Singles". These are where there is only one "option" in a cell. You can safely enter this as the "cell solution" in such a situation. Update the surrounding cells "options" to match. Repeat the "Single" search throughout the Sudoku puzzle.
3. Next, is the slighter more complicated search for "Hiddne Singles". These are where there is only one option for a row, column, or sub-square, but is hidden within others. To find "Hidden Singles"; look in a row, column, or sub-square for only one occurence of an "option". In this example, the "hidden single" would be 1 as no other option in the square is 1. Repeat for all occurences of "Hidden Singles" in the Sudoku square.
4. Use your general intuition to complete the Sudoku.

That concludes the basic method. Harder techniques involving "Locked", and "Naked" manipulation are available, but are beyond the scope of this article.

Try it out for yourself

It doesn't matter how long you study strategies, to truly become 'good' at Sudoku, you need to play Sudoku. Hence:

Discuss Sudoku in the forum/a>.