The Solver window

The Solver window is opened by clicking on the Solver tool on the toolbar. Click on the Solve button to solve the current puzzle using the methods ticked. The time taken will be displayed and the number of times each solving method was used will be shown.

You may tick and untick different methods to try solving a puzzle in different ways. For most puzzles you will need more than one method. In the Choices window you may choose to have hints also given according to which methods you have ticked in the Solver window. With this setting, if the only way to fill in a square requires a method which is not ticked, no hint will be given.

Click on the information button to view this help page.

The solving methods

Only possible location in area

Look at all the values missing from a row, column or block. If one of them has only one possible location in the row, column or block, put it in.

Sole possibility for square

Look at a single square and consider which values are possible, eliminating those already used in the same row, column or block. If only one value is possible, put it in.

Pairs, triples, etc.

Look at a row, column or block. If there is a set of n blank squares which between them have only n different values as possible solutions, these values must occupy these squares and so cannot appear elsewhere in that area. After removing these values from consideration for the other blank squares in that area, see whether this leads to a solution to another square by one of the simpler methods.

Intersecting areas

Look at a row or column and consider an unused value. If all the possible locations for that value in the row or column fall in the same block, none of the other blank squares in that block can have this value. Eliminate this value from the possible solutions for them and see whether this leads to a solution by one of the simpler methods.

Or similarly, look at a block and consider an unused value. If all the possible locations for that value in the block fall in the same row or column, none of the other squares in that row or column can have this value.

Trial and error

This is the slow, "hit and miss" method of solving by eliminating the impossible, which is much easier for a computer to do than a human. A square with only a few possible values is chosen, and each of those values tried in turn. Those values which lead to a contradiction are eliminated.

Note that trial and error will not fill in a puzzle which has more than one possible solution, but SuperDoku may spend a long time thinking about it before giving up.


Main SuperDoku help page