KenKen puzzle solver.
KenKen puzzles are supposed to be NP complete, as they can be reduced
from Sudoku puzzles which are also NP complete. But according to Will
Shortz, the editor of a collection of KenKen puzzles I own, there should
be a path of logic that you can follow through every KenKen puzzle
and guess and check isn't necessary. This doesn't sound NP-complete to me,
so part of my goal in this project is to figure out if there is a special
case of KenKen that can be solved in time P, and if this special case is
really what we see in most of the puzzles we solve.