Sudoku

I've recently learned how to play Sudoku. Below is my first really difficult one involving bifurcation.

My first difficult Sudoku     3   2   1           4   6   5   7       8       9   9       8   7           4           1   2       9   6       5       4   2 4 3   1           8   7   6

Tina was able to solve the one above without any backtracking so I'll have to revisit it yet again! Another interesting thing she said which has rekindled my interest in Sudoku is that you should never have to use backtracking, there should always be a purely logical reason for every number to be filled in uniquely otherwise it defeats the purpose of Sudoku.

I revisited the one above yet again, and this time was able to complete it without requiring any difficult logic, so I must have not been meticulous enough writing in or checking the possibilities the first.

See also

• Wikipedia:Sudoku
• DailySudoku - blank grids can be downloaded and printed from here