Solves any level sudoku
Input puzzle ex:-
'.7.5....4.....698.6....42.7.....2.9.3.4.9.7.2.9.1.....9.84....5.356.....7....8.4.'
(Taken from http://www.7sudoku.com/view-puzzle?date=20161025)
Soln:
2 7 9 5 8 3 1 6 4 5 4 1 7 2 6 9 8 3 6 8 3 9 1 4 2 5 7 1 5 7 3 6 2 4 9 8 3 6 4 8 9 5 7 1 2 8 9 2 1 4 7 5 3 6 9 2 8 4 3 1 6 7 5 4 3 5 6 7 9 8 2 1 7 1 6 2 5 8 3 4 9