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If the solution is unique then there is a logical path to it, though maybe not one feasible to discover for an agent with bounded time and (especially for humans) bounded working m…

> A more reasonable question would be, how many partially completed sudoku grids are there which have a unique solution. We don't know the answer to that. The number of minimal Sud…

For a casual effort this solver is quite fast. On most datasets it's significantly faster than a C++ port of the Norvig solver and it's often in the same league as well-tuned DLX s…

I think neel_k was referring to the fact that when a DPLL or CDCL solver concludes UNSAT you can take the trace its backtracking activity and rewrite it from the bottom up as a res…

Sudoku may be a poor example for illustrating some of the overarching points of this series of blog posts, which I take to be that modern SAT solvers are, as someone described them…

Bear in mind that JSolve was 5x faster than the fastest DLX solver in the attractivechaos 2011 benchmarks, and today there are several solvers that are 2x faster than JSolve ( http…

This sounds like Crook's Algorithm ( https://www.ams.org/notices/200904/tx090400460p.pdf ), which is a perfectly reasonable thing to do, especially for pencil-and-paper puzzle solv…

It's easy to see why this puzzle has no solution. Looking at columns 4-6 we see that none of the digits 1,5,6 can occur in cells G4,H4,I4 or G6,H6,I6. So some permutation of these …

It can be done with just depth first search, but if you want it to be fast you can go pretty far down the rabbit hole. The details of your representation, your heuristics, and the …

I'm the author of Tdoku and maintainer of those benchmarks. If anyone has a well optimized DLX implementation I'd love to add it to the comparison. The few I've sampled from github…