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Klaus Wittrock


Games::Sudoku::Trainer::Nextvalue - get some new value while solving a Sudoku puzzle


This part of the documentation for SudokuTrainer aims at people that just want some new value to get over an obstacle while solving a Sudoku puzzle. If this isn't what you expected, please inspect section "GUIDE TO DOCUMENTATION" in the dokumentation for SudokuTrainer (use "perldoc sudokutrainer.pl").


    perldoc Games::Sudoku::Trainer::Nextvalue


I presume that you like to solve Sudoku puzzles, but don't proceed "professionally" by applying Sudoku solution strategies. Instead you search intuitively for cells where only one digit remains allowed. Sometimes it happens that after a while you cannot assign a further digit to a cell. Here this program SudokuTrainer can often help you.


When starting SudokuTrainer you have to enter the Sudoku puzzle for which you need help. Therefore you select the option Insert manually. If you cannot find out how the input works, you may read the documentation of enter_presets.pl (use "perldoc enter_presets.pl"). When finished with the input you click the Button Done and thus reach the main window of SudokuTrainer. There you should save the entered puzzle first, just in case you need it again later. For this you use the menu File -> Save initial puzzle. You may catch up this step at any time lateron.


You may use the option Insert manually also for editing a stored Sudoku puzzle, e. g. for correcting an error. For this you click the Button Edit puzzle while the Sudoku board is empty, then select the file of the puzzle. The changed puzzle is then used as a new puzzle.


This is easy if you have entered all already known values, i. e. the preset values as well as the already found ones. Select menu Pause mode -> value found -> anywhere and click the Run Button. SudokuTrainer finds the first new value, but displays nothing but the strategy that found it. Click the Run Button again. SudokuTrainer finds the next new value, and in addition displays the previous one with a black frame around it. With this value you may try to solve your Sudoku puzzle further.

The only problem is: One of the values that you found might be wrong. Then the new value given by SudokuTrainer is uncertain. You can check this afterwards: Select menu Pause mode -> non-stop and click the Run Button once. When your puzzle gets solved completely now, everything is ok. If not, one of your values might be wrong. Here a stepwise procedure is required.

Either start from scratch and enter only the preset values of your puzzle, or remove all values that you found, as described in section EDIT A SUDOKU PUZZLE. Then select menu Pause mode -> value found -> anywhere repeatedly until the value displayed in the black frame wasn't already found by you. With this value you may try to solve your Sudoku puzzle further.


At the start of this document I presumed that you don't know about Sudoku solution strategies. This isn't really true. You use at least intuitivily the easiest strategies, maybe without knowing their names. I will show them here shortly.

Full house

In a unit there is only one cell left free. So the still remaining value belongs to this cell.

Hidden single

In a unit a certain candidate is permitted in one cell only. So this candidate belongs to this cell. In this cell there are usually further candidates, among which this value is hidden.

Naked single

In a cell there is only one candidate permitted. So this is the value for this cell. This strategy is considerably more rarely than the first ones, and it is distinctly more difficult to find. Some Sudoku friends maintain a candidate list for this. The SudokuTrainer will save you a lot of hard work, when you use the menu View to display the internal candidate list.

Make use of the History

The knowledge of these three easiest strategies opens a further option of getting help by SudokuTrainer: Use the preset values only when entering the Sudoku puzzle, select menu Pause mode -> non-stop and click the Run Button. When then the list History -> Summary consists of only these three strategies, you will know that you truely can solve your Sudoku puzzle completely by yourself. When Naked single is there too, you may look up at History -> Overview the steps where you have to pay attention to this strategy.