caderoux,

I presume that you are using Simple Sudoku. The program only has so many human ready hints available. That is, if the sudoku "requires" more than hidden and naked sets, intersection removal (which it calls locked candidates) x-wings, xy-wings, coloring and multicoloring, eventually, Simple Sudoku will run out of hints. That is not to say that it can't solve it. It already has, just not using the above patterns.

In your puzzle, the candidate grid should be

- Code: Select all
` 23 7 5| 9 1 268 | 346 3468 368| `

8 1 6| 4 3 5 | 9 2 7 |

4 23 9| #268 #268 7 | 1 368 5 |

-----------+-----------------+-------------|

57 -45 3| #68 #5678 9 | 2 468 1 |

79 6 1| 238 278 2348 | 34 5 389|

25 2459 8| 1 56 346 | 7 3469 36 |

-----------+-----------------+-------------|

1 39 7| 5 28 28 | 36 369 4 |

369 8 2| 36 4 1 | 5 7 39 |

356 35 4| 7 9 36 | 8 1 2 |

*----------+-----------------+-------------|

Notice that the cells in (3,[45]) and (4,[45]) will form a deadly pattern on <68> if

(3,[45])!2 and (

4,5)![57] . But (4,2)5 implies

(4,5)!5 and it implies that (4,1)7 >

(4,5)!7. Moreover, (4,1)7 > (6,1)2 > (1,1)3 > (3,2)2 >

(3,[45])!2 . Therefore, (4,2)4.

This does not solve the puzzle completely, but it gets you back to a point where Simple Sudoku can give you hints.