CSP Sudoku Solver
Constraint satisfaction solver using backtracking, AC-3 arc consistency, and MRV heuristic for efficient puzzle solving.
The Problem
Brute-forcing a hard Sudoku is slow. With the right constraint propagation, most puzzles collapse to a solution with little or no backtracking.
Architecture & Approach
Constraint satisfaction with backtracking, AC-3 arc consistency preprocessing, and MRV heuristic for intelligent variable ordering.
Key Technical Decisions
AC-3 arc consistency before any search
Propagating constraints first strips impossible values from every cell up front. Many puzzles fall out from propagation alone, and the rest start from a much smaller search space.
MRV heuristic for variable ordering
When search is still needed, filling the cell with the fewest remaining candidates first fails fast on dead ends and keeps the branching factor low, instead of marching through the grid in row order.
Results
Solve any grid in the browser. The Solve button runs the CSP solver and fills a valid solution in well under a second.