Applied Mathematics

It is commonly understood that with sudoku puzzles, the more starter numbers you are given, the easier the puzzle will be, but this is not necessarily the case. Some of the easy puzzles in Sudoku magazine have just as many starter digits as the hard puzzles.

Another idea that is commonly held to be true is that the minimum number of starter digits required to produce a sudoku with a unique solution is 17. I have to trust the mathematicians, here. Certainly, I've never seen a sudoku with fewer starter digits and I don't have the expertise to challenge their findings.

This brings me to the latest findings of two mathematicians, Dr Paul Newton and Stephen DeSalvo of the University of Southern California in Los Angeles. They have discovered that sudoku matrices are more random than randomly generated arrays. Based on the theory that sudoku puzzles with fewer starter numbers are harder, they believe that their findings will help sudoku compilers create better algorithms for constructing sudoku puzzles, and potentially create puzzles with fewer starter digits than 17 – and therefore, possibly, more challenging puzzles.

The difficult puzzles in Sudoku magazine are hand-made for humans. Computer-generated hard puzzles are probably best solved by computers. The prospect of more difficult sudoku puzzles than those we publish does not appeal – we can't all think like computers, or mathematicians!