Sudoku solver program, do it like a human!

[User137]

I also have made a sudoku solver, that you can possibly learn from
Lazarus source: https://www.dropbox.com/s/u27owmiqrb...u_src.zip?dl=0
Windows binary: https://www.dropbox.com/s/e95blmhhti...udoku.zip?dl=0

Actual solver is recursive, nothing human related. Quick and deep scan of all possible choices, it will also display all of them (normal "proper" sudokus are built with only 1 solution though). So if any sudoku has a solution, this will find it.

But there is a bit more that human-like when building a new sudoku from scratch. First it fills the table, with algorithm i don't remember in detail, but then it starts clearing it. Each cell can have calculated a value, of how many possible numbers it can have based on the numbers already set on board. If for example the row 1 already has number 4, then none of the other 8 cells on that row can have 4, the normal gamerule check. The generator keeps track of that for each cell, and also of what those numbers are. It goes through the whole grid and then finds which ones have lowest value, then randomly picks 1 of the winners and makes it blank. Repeat until number density (filled:empty ratio) reaches the wanted difficulty level, where closest to empty is hardest. When you think about it, a cell that has low value is easy for human to figure out, so it's quite balanced on the difficulty.

edit: Lowest value, not highest... i think