Solve sudoku using the cp module in Picat (http://picat-lang.org/)

sudoku.pi

import cp.   % ::, all_different
import util. % transpose

write_sudoku(S) =>
  foreach (R in S)
    foreach (X in R)
      printf("%d ", X)
    end,
    printf("%n")
  end.

sudoku(S) =>
  S :: 1 .. 9,
  foreach (R in S)
    all_different(R)
  end,
  foreach (C in transpose(S))
    all_different(C)
  end,
  foreach (CR in 0 .. 2, CC in 0 .. 2)
    Cell = [S[3 * CR + I, 3 * CC + J] : I in 1 .. 3, J in 1 .. 3],
    all_different(Cell)
  end,
  solve(S).

main =>
  S = { {8, _, _, _, _, _, _, _, _}
      , {_, _, 3, 6, _, _, _, _, _}
      , {_, 7, _, _, 9, _, 2, _, _}
      , {_, 5, _, _, _, 7, _, _, _}
      , {_, _, _, _, 4, 5, 7, _, _}
      , {_, _, _, 1, _, _, _, 3, _}
      , {_, _, 1, _, _, _, _, 6, 8}
      , {_, _, 8, 5, _, _, _, 1, _}
      , {_, 9, _, _, _, _, 4, _, _}
      },
  time2(sudoku(S)),
  write_sudoku(S).