Minimal Problems

The Sudoku application provides the possibility to generate "minimal" problems. These problems are created in way that all of the pre-allocated values are needed for an unambiguous solution. The example at the right show a not minimized Sudoku and its minimized version. The minimized version has only 22 pre-allocation whereas the not minimized version has two additional pre-allocations (the 2 in the cell in row 1, column 6 and the 9 in row 8, column 8).


Minimized Sudoku
Not minimized Sudoku

Minimization does not necessarily change the severity level of a problem, but in most cases minimal problems are harder than their "normal" origin.

Both, newly generated problems and existing problems can be minimized. The former is controlled by the respective option, the later can be enforced either by selecting the menu entry "Problem|Find Minimal Allocation" or by pressing <F9>.

Currently normal Sudokus with only 17 pre-allocations and X-Sudokus with only 12 pre-allocations are known.