# main ``` python import numpy as np import time from sudoku.cell import * from sudoku.board import * ``` You can create a Board from a list of 9 lines of 9 chars each. Legal chars are the numbers from 1 to 9 and - for empty cell ``` python # medium board = ['5-------6', '-816---5-', '--2-5-14-', '----7--3-', '--71-69--', '-1--3----', '-26-4-7--', '-5---249-', '8-------2'] b = Board(board) ``` ``` python def foo(): board_wrong_format_1 = ['---------', '---------', '----7--3-', '--71-----', '-1--3----', '-26-4-7--', '-5-------', '8--------'] return Board(board_wrong_format_1) test_fail(foo) ``` ``` python def foo2(): board_wrong_format_2 = ['---------', '---------'] return Board(board_wrong_format_1) test_fail(foo2) ``` A board can be exported, generating a line of text which can be imported in external sites, like [Sudoku solutions](https://www.sudoku-solutions.com/) ``` python b.export() ``` '5 6 816 5 2 5 14 7 3 71 69 1 3 26 4 7 5 249 8 2' ``` python # hard board = ['----5163-', '----94---', '--3-6--94', '6-7------', '-386--5--', '9-1------', '--6-1--57', '----26---', '----3786-'] b = Board(board) ``` You can try to solve a board: ``` python b.solve() ``` |0--|1--|2--|3--|4--|5--|6--|7--|8--| 0| 4 | 8 | 9 | 7 | 5 | 1 | 6 | 3 | 2 | 1| 7 | 6 | 2 | 3 | 9 | 4 | 1 | 8 | 5 | 2| 5 | 1 | 3 | 8 | 6 | 2 | 7 | 9 | 4 | 3| 6 | 5 | 7 | 1 | 4 | 3 | 9 | 2 | 8 | 4| 2 | 3 | 8 | 6 | 7 | 9 | 5 | 4 | 1 | 5| 9 | 4 | 1 | 2 | 8 | 5 | 3 | 7 | 6 | 6| 3 | 9 | 6 | 4 | 1 | 8 | 2 | 5 | 7 | 7| 8 | 7 | 5 | 9 | 2 | 6 | 4 | 1 | 3 | 8| 1 | 2 | 4 | 5 | 3 | 7 | 8 | 6 | 9 | |0--|1--|2--|3--|4--|5--|6--|7--|8--| To solve a very hard puzzle, chances are you will need to use brute force ``` python # very hard 1 board = ['8-----41-', '-6-9-----', '3-2------', '-5---814-', '4----1--3', '-8---326-', '1-9------', '-7-3-----', '2-----85-'] b = Board(board) ``` ``` python # very hard 2 board = ['4-------8', '--9-1--7-', '-23--54--', '-----26--', '-9--5--4-', '--71-----', '--24--39-', '-7--6-5--', '1-------4'] b = Board(board) ``` ``` python b = Board(board) res = b.solve() test_eq(res, Solution.NOT_FOUND) res.value ``` |0-----------|1-----------|2-----------|3-----------|4-----------|5-----------|6-----------|7-----------|8-----------| 0| 4 | 1---56---| 1---5----| 2 | --3---7--| --3--67--| 9 | --3-5----| 8 | 1| ----56-8-| ----56-8-| 9 | --3--6---| 1 | 4 | 2 | 7 | --3-5----| 2| 7 | 2 | 3 | -------89| -------89| 5 | 4 | 1----6---| 1----6---| 3| --3-5--8-| 1--45--8-| 1---5----| --3---789| --34---89| 2 | 6 | --3-5----| --3-5-7-9| 4| 2 | 9 | -----6-8-| --3--678-| 5 | --3--6-8-| 1 | 4 | --3---7--| 5| --3-56---| ---456---| 7 | 1 | --34----9| --3--6---| 8 | 2 | --3-5---9| 6| ----56-8-| ----56-8-| 2 | 4 | ------78-| 1-----78-| 3 | 9 | 1----6---| 7| 9 | 7 | 4 | --3----8-| 6 | 1-3----8-| 5 | 1------8-| 2 | 8| 1 | 3 | -----6-8-| 5 | 2 | 9 | 7 | -----6-8-| 4 | |0-----------|1-----------|2-----------|3-----------|4-----------|5-----------|6-----------|7-----------|8-----------| 'solution not found' ``` python b = Board(board) res = b.solve(True, print_log = True) test_eq(res, Solution.ONE_SOLUTION) res.value ``` 0 *** single candidate row 1: filled cell [1, 5] with value 4 1 *** single candidate row 7: filled cell [7, 2] with value 4 2 *** single candidate column 3: filled cell [8, 3] with value 5 3 *** single candidate column 0: filled cell [2, 0] with value 7 4 *** single candidate column 0: filled cell [7, 0] with value 9 5 *** single candidate block 6: filled cell [8, 1] with value 3 6 *** lone single: filled cell [1, 6] with value 2 7 *** pointing group of 1 in block 0 to row 0: removed candidate 1 from cell [0, 7] 8 *** pointing group of 1 in block 0 to row 0: removed candidate 1 from cell [0, 6] 9 *** pointing group of 8 in block 0 to row 1: removed candidate 8 from cell [1, 3] 10 *** pointing group of 1 in column 6 to block 5: removed candidate 1 from cell [4, 8] 11 *** pointing group of 1 in column 6 to block 5: removed candidate 1 from cell [3, 8] 12 *** pointing group of 1 in column 6 to block 5: removed candidate 1 from cell [3, 7] 13 *** pointing group of 1 in row 3 to block 3: removed candidate 1 from cell [4, 2] 14 *** hidden group of {1, 5} in column 2: removed candidates {8} from cell [3, 2] 15 *** hidden group of {1, 5} in column 2: removed candidates {6} from cell [0, 2] 16 *** hidden group of {3, 5} in block 2: removed candidates {6} from cell [1, 8] 17 *** hidden group of {3, 5} in block 2: removed candidates {6} from cell [0, 7] 18 *** hidden group of {1, 6} in block 2: removed candidates {9} from cell [2, 8] 19 *** hidden group of {8, 9} in row 2: removed candidates {6} from cell [2, 3] 20 *** single candidate row 4: filled cell [4, 6] with value 1 21 *** single candidate column 6: filled cell [8, 6] with value 7 22 *** single candidate column 6: filled cell [5, 6] with value 8 23 *** single candidate column 6: filled cell [0, 6] with value 9 24 *** naked group of {1, 6} in column 8: removed candidates {1} from cell [7, 8] 25 *** naked group of {3, 5} in column 7: removed candidates {3, 5} from cell [5, 7] 26 *** lone single: filled cell [5, 7] with value 2 27 *** lone single: filled cell [7, 8] with value 2 28 *** naked group of {8, 6} in row 8: removed candidates {8} from cell [8, 5] 29 *** naked group of {8, 6} in row 8: removed candidates {8} from cell [8, 4] 30 *** pointing group of 2 in column 3 to block 1: removed candidate 2 from cell [0, 4] 31 *** single candidate row 0: filled cell [0, 3] with value 2 32 *** single candidate row 4: filled cell [4, 0] with value 2 33 *** single candidate row 8: filled cell [8, 4] with value 2 34 *** single candidate row 8: filled cell [8, 5] with value 9 35 *** pointing group of 7 in column 3 to block 4: removed candidate 7 from cell [4, 5] 36 *** pointing group of 7 in column 3 to block 4: removed candidate 7 from cell [3, 4] 37 ****** trying brute force, removing candidate 1 from cell [0, 2] 38 ****** Before brute force: |0-----------|1-----------|2-----------|3-----------|4-----------|5-----------|6-----------|7-----------|8-----------| 0| 4 | 1---56---| ----5----| 2 | --3---7--| --3--67--| 9 | --3-5----| 8 | 1| ----56-8-| ----56-8-| 9 | --3--6---| 1 | 4 | 2 | 7 | --3-5----| 2| 7 | 2 | 3 | -------89| -------89| 5 | 4 | 1----6---| 1----6---| 3| --3-5--8-| 1--45--8-| 1---5----| --3---789| --34---89| 2 | 6 | --3-5----| --3-5-7-9| 4| 2 | 9 | -----6-8-| --3--678-| 5 | --3--6-8-| 1 | 4 | --3---7--| 5| --3-56---| ---456---| 7 | 1 | --34----9| --3--6---| 8 | 2 | --3-5---9| 6| ----56-8-| ----56-8-| 2 | 4 | ------78-| 1-----78-| 3 | 9 | 1----6---| 7| 9 | 7 | 4 | --3----8-| 6 | 1-3----8-| 5 | 1------8-| 2 | 8| 1 | 3 | -----6-8-| 5 | 2 | 9 | 7 | -----6-8-| 4 | |0-----------|1-----------|2-----------|3-----------|4-----------|5-----------|6-----------|7-----------|8-----------| 39 ****** trying brute force, removing candidate 5 from cell [0, 2] 40 ****** Before brute force: |0-----------|1-----------|2-----------|3-----------|4-----------|5-----------|6-----------|7-----------|8-----------| 0| 4 | 1---56---| 1--------| 2 | --3---7--| --3--67--| 9 | --3-5----| 8 | 1| ----56-8-| ----56-8-| 9 | --3--6---| 1 | 4 | 2 | 7 | --3-5----| 2| 7 | 2 | 3 | -------89| -------89| 5 | 4 | 1----6---| 1----6---| 3| --3-5--8-| 1--45--8-| 1---5----| --3---789| --34---89| 2 | 6 | --3-5----| --3-5-7-9| 4| 2 | 9 | -----6-8-| --3--678-| 5 | --3--6-8-| 1 | 4 | --3---7--| 5| --3-56---| ---456---| 7 | 1 | --34----9| --3--6---| 8 | 2 | --3-5---9| 6| ----56-8-| ----56-8-| 2 | 4 | ------78-| 1-----78-| 3 | 9 | 1----6---| 7| 9 | 7 | 4 | --3----8-| 6 | 1-3----8-| 5 | 1------8-| 2 | 8| 1 | 3 | -----6-8-| 5 | 2 | 9 | 7 | -----6-8-| 4 | |0-----------|1-----------|2-----------|3-----------|4-----------|5-----------|6-----------|7-----------|8-----------| 41 *** PUZZLE SOLVED WITH BRUTE FORCE |0--|1--|2--|3--|4--|5--|6--|7--|8--| 0| 4 | 6 | 1 | 2 | 3 | 7 | 9 | 5 | 8 | 1| 5 | 8 | 9 | 6 | 1 | 4 | 2 | 7 | 3 | 2| 7 | 2 | 3 | 9 | 8 | 5 | 4 | 1 | 6 | 3| 8 | 1 | 5 | 7 | 4 | 2 | 6 | 3 | 9 | 4| 2 | 9 | 6 | 8 | 5 | 3 | 1 | 4 | 7 | 5| 3 | 4 | 7 | 1 | 9 | 6 | 8 | 2 | 5 | 6| 6 | 5 | 2 | 4 | 7 | 8 | 3 | 9 | 1 | 7| 9 | 7 | 4 | 3 | 6 | 1 | 5 | 8 | 2 | 8| 1 | 3 | 8 | 5 | 2 | 9 | 7 | 6 | 4 | |0--|1--|2--|3--|4--|5--|6--|7--|8--| 'found a solution' The solver detects a puzzle with no solutions ``` python already_inconsistent_board = ['4--4----8', '--9-1--7-', '-23--54--', '-----26--', '-9--5--4-', '--71-----', '--24--39-', '-7--6-5--', '1-------4'] b = Board(already_inconsistent_board) res = b.solve() test_eq(res, Solution.NO_SOLUTIONS) res.value ``` 'no solutions' ``` python board_no_solutions = ['4-52--9-8', '--9-1427-', '723--54--', '-----26--', '29--5-14-', '--71--82-', '--24--39-', '974-6-5-2', '13-5297-4'] b = Board(board_no_solutions) res = b.solve() test_eq(res, Solution.NO_SOLUTIONS) res.value ``` 'no solutions' Trying to solve a puzzle with more than one solution, the solver picks one of them (you’ll need to use brute force) ``` python board_many_solutions = ['123456789', '---------', '---------', '---------', '---------', '---------', '---------', '---------', '---------'] b = Board(board_many_solutions) res = b.solve(True) test_eq(res, Solution.ONE_SOLUTION) res.value ``` |0--|1--|2--|3--|4--|5--|6--|7--|8--| 0| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 1| 7 | 6 | 5 | 9 | 1 | 8 | 4 | 3 | 2 | 2| 4 | 9 | 8 | 7 | 3 | 2 | 6 | 5 | 1 | 3| 6 | 1 | 7 | 2 | 4 | 5 | 8 | 9 | 3 | 4| 5 | 8 | 4 | 1 | 9 | 3 | 2 | 6 | 7 | 5| 9 | 3 | 2 | 6 | 8 | 7 | 5 | 1 | 4 | 6| 3 | 7 | 9 | 5 | 6 | 4 | 1 | 2 | 8 | 7| 2 | 5 | 1 | 8 | 7 | 9 | 3 | 4 | 6 | 8| 8 | 4 | 6 | 3 | 2 | 1 | 9 | 7 | 5 | |0--|1--|2--|3--|4--|5--|6--|7--|8--| 'found a solution' However, you can check the existence of more than one solution ``` python b = Board(board_many_solutions) res = b.solve(True, print_log=True, check_many_solutions=True) test_eq(res, Solution.MULTIPLE_SOLUTIONS) res.value ``` 0 ****** trying brute force, removing candidate 4 from cell [1, 0] 1 ****** Before brute force: |0-----------|1-----------|2-----------|3-----------|4-----------|5-----------|6-----------|7-----------|8-----------| 0| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 1| ----56789| ---456789| ---456789| 123---789| 123---789| 123---789| 123456---| 123456---| 123456---| 2| ---456789| ---456789| ---456789| 123---789| 123---789| 123---789| 123456---| 123456---| 123456---| 3| -23456789| 1-3456789| 12-456789| 123-56789| 1234-6789| 12345-789| 123456-89| 1234567-9| 12345678-| 4| -23456789| 1-3456789| 12-456789| 123-56789| 1234-6789| 12345-789| 123456-89| 1234567-9| 12345678-| 5| -23456789| 1-3456789| 12-456789| 123-56789| 1234-6789| 12345-789| 123456-89| 1234567-9| 12345678-| 6| -23456789| 1-3456789| 12-456789| 123-56789| 1234-6789| 12345-789| 123456-89| 1234567-9| 12345678-| 7| -23456789| 1-3456789| 12-456789| 123-56789| 1234-6789| 12345-789| 123456-89| 1234567-9| 12345678-| 8| -23456789| 1-3456789| 12-456789| 123-56789| 1234-6789| 12345-789| 123456-89| 1234567-9| 12345678-| |0-----------|1-----------|2-----------|3-----------|4-----------|5-----------|6-----------|7-----------|8-----------| |0-----------|1-----------|2-----------|3-----------|4-----------|5-----------|6-----------|7-----------|8-----------| 0| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 1| ---456789| ---456789| ---456789| 123---789| 123---789| 123---789| 123456---| 123456---| 123456---| 2| ---456789| ---456789| ---456789| 123---789| 123---789| 123---789| 123456---| 123456---| 123456---| 3| -23456789| 1-3456789| 12-456789| 123-56789| 1234-6789| 12345-789| 123456-89| 1234567-9| 12345678-| 4| -23456789| 1-3456789| 12-456789| 123-56789| 1234-6789| 12345-789| 123456-89| 1234567-9| 12345678-| 5| -23456789| 1-3456789| 12-456789| 123-56789| 1234-6789| 12345-789| 123456-89| 1234567-9| 12345678-| 6| -23456789| 1-3456789| 12-456789| 123-56789| 1234-6789| 12345-789| 123456-89| 1234567-9| 12345678-| 7| -23456789| 1-3456789| 12-456789| 123-56789| 1234-6789| 12345-789| 123456-89| 1234567-9| 12345678-| 8| -23456789| 1-3456789| 12-456789| 123-56789| 1234-6789| 12345-789| 123456-89| 1234567-9| 12345678-| |0-----------|1-----------|2-----------|3-----------|4-----------|5-----------|6-----------|7-----------|8-----------| 'multiple solutions'