Contains function to return dependency score of a Sudoku board to be used to calculate difficulty.
Inspired by https://www.fi.muni.cz/~xpelanek/publications/flairs-sudoku.pdf
Calculates difficulty based on the dependencies of the steps used to solve the board.
Calculates dependency score by counting how many applications of simple strategies are available at each step.
So if a puzzle has an average of 6 obvious/hidden singles available at each step then it is easier to solve than a puzzle where there is only an average of two obvious/hidden singles at each step.
WARNING: This assumes that the number of givens is the same for the boards being compared.
For example, you could have a board that is really harder but has fewer givens so there are more obvious/hidden singles available at each step due to more cells being empty total.
Multiplied by negative 1 to get a positive correlation between difficulty and dependency score.
Contains function to return dependency score of a Sudoku board to be used to calculate difficulty. Inspired by https://www.fi.muni.cz/~xpelanek/publications/flairs-sudoku.pdf Calculates difficulty based on the dependencies of the steps used to solve the board. Calculates dependency score by counting how many applications of simple strategies are available at each step. So if a puzzle has an average of 6 obvious/hidden singles available at each step then it is easier to solve than a puzzle where there is only an average of two obvious/hidden singles at each step. WARNING: This assumes that the number of givens is the same for the boards being compared. For example, you could have a board that is really harder but has fewer givens so there are more obvious/hidden singles available at each step due to more cells being empty total. Multiplied by negative 1 to get a positive correlation between difficulty and dependency score.