Line
Colunm Block

The principle of Sudoku is that in each line, column and block,
a number between 1 and 9 could only be used one time. At crossing of line,
columns or block, value of the cell are limited. By looking at each cell
systematically (roughly) or by identifying the promising cells, it's easy to
find the missing number.

Single

For a block, we have to verify all lines
and columns owning already a given number. By crossing, we can eliminate cells
and found the only one where this number is possible.

Probable

In a block, if there are only 2 possible cells for a given number, their
value become Probable. Use of Probable in cells allows to simplify the
resolution.

Group

In a line, if there are 2 cells which can only have the 2
same numbers, so these 2 numbers can not be on the other cells of the line. This
can be expanded on at groups of 3 to 7 numbers, corresponding respectively to 3
to 7 cells.

Coloring Chain 
By forming possible chain for a given number, it
highlights rows, columns or block having a only one possible value.

Forcing Chain 
By checking for a given cell, all possible
combinations, we can identify other grid cells with only
one possible value.

Burma 
For a given number, we can search at cross of lines columns
blocks (2 dimensions) with the same or less number of cells available for
this number. You can delete the other possibles.

Random

In a cell with 2 possible numbers, we
can choose one at random, and then we continue. If we arrive to an error or
unavoidability, a come back is necessary because it means that the second
number is the good one.

Variant 
According to the variant used, a filter is
implemented in order to seek the solution to solve the variant.
