from Hacker News

Swift Sudoku Solver

by astigsen on 11/13/17, 11:22 PM with 4 comments

• by MekaiGS on 11/14/17, 12:06 AM

  As the author mentioned, it cannot solve any boards where all unfilled cells have more than one possible value within the cell's domain. More information about the algorithm here:

  https://en.wikipedia.org/wiki/AC-3_algorithm

  You would need to implement something like forward checking or backtracking algorithm to solve all possible boards with higher cost.