15 Nov
2006
15 Nov
'06
9:50 p.m.
I don't comment often here, but two comments. 1. The sudoku you posted has more than one solution. 2. Hardest in the context under discussion ususally means "hardest for a person". This corrolates a bit with backtracking difficulty, but it only corrolates. Making a precise measure of "human difficulty" is difficult. Doug