The Generator relies on taking away squares from a completed puzzle and assigning each square a SE Rating based on the hardest technique needed to "put the square back". It then stacks up all these ratings for the whole puzzle.

This technique has a definite weakness towards sharing a single high rating technique's score amoungst several undeserving squares because all replacement routes funnel through a common high rating square. So far, so fair enough.

Here's the issue - I've recently added code to remember the top five square ratings for a puzzle. Theoretically the very highest square should equal the Sudoku Explainer rating. BUT IT DOESN'T.

QUESTION - Is it possible to reduce the Sudoku Rating of an unoptimised puzzle (one in which there are still redundant squares) by removing these squares?

As an example, the puzzle:

- Code: Select all
`000060100`

080750000

009000000

020000000

610870005

053000060

042000000

000023008

030010400

Puzzle Rating = 1313

Top 5 square ratings are: 50 50 50 54 54

Has (presumably) identified at least two different squares that require a Quad to replace (One Naked Quad and one Hidden Quad). When plugged into Sudoku Explainer though, the highest rated technique is a Naked Triplet.

Do I have to accept that there is a serious error in my technique spotting code or is it possible that by taking away more squares, the Hidden Quad has (possibly by allowing a number of mid-ranged techniques) been reduced to a Naked Triplet?

EDIT - Because my code evaluates all twins at a given level at the same time, it is possible that the Hidden Quad was actually a Naked Quad. Even so, it was still a Quad.