I have created a standard sudoku solver using my own algorithm. It relies on a continuous scanning with occasional tuple/pair searching. I am looking forward to test if this works properly. I have hand tested it one some Evil puzzles.

Is there any source where I can get extremely hard standard sudoku puzzle's (having a unique solution) to test out my solver?

  • $\begingroup$ You may be able to find a suitable open-source sudoku generator. $\endgroup$ Commented Jun 1, 2020 at 23:05
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    $\begingroup$ projecteuler.net/problem=96 $\endgroup$
    – Dr Xorile
    Commented Jun 1, 2020 at 23:09
  • $\begingroup$ Do the puzzles have to be extremely hard? As far as I know (I never tried), it is possible to enumerate sudoku arrangements by backtracking, and then you can add clues from that arrangement onto an empty grid in random places until a different sudoku solver reports an unique solution. $\endgroup$ Commented Jun 2, 2020 at 3:41
  • $\begingroup$ well by extremely hard I meant where there are less clues, to check if I missed any logic, as I didn't use backtracking and was trying something on my own. I tried to simulate human solving techniques like using pencil marks, finding naked singles, finding full house/last digit, finding hidden pair etc. $\endgroup$ Commented Jun 2, 2020 at 19:33
  • $\begingroup$ Is this really classified as a puzzle? $\endgroup$ Commented Jun 3, 2020 at 2:41

1 Answer 1


In addition to the Project Euler Problem 96 that Dr Xorile has linked in their comment:


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