OOP based C++ sudoku solver. Implements the following algorithms (see http://www.sadmansoftware.com/sudoku/solvingtechniques.htm for explanations and examples): naked single, hidden single, block row/column interaction, block block interaction, naked subset and hidden subset.

Usage: Write in sudoku.txt all 81 cells, 9 cells per line, using a period for unknown cells. For example

4.18..3.2
..8.6....
......9..
..7..5.3.
.5.974.1.
.1.3..5..
..9......
....9.1..
8.3..17.5

Or, write in sudoku.txt all 81 cells in a single line, left to right, top to bottom, using a period for unknown cells. For example

4.18..3.2..8.6..........9....7..5.3..5.974.1..1.3..5....9..........9.1..8.3..17.5