Samer_sadek,

Not sure to which of the techniques mentioned in the other forum you are referring. The thing about the 9's (by geoff h) is called either locked candidates or row-box interaction. Basically the only place for a 9 in row 4 is in box 6. If any cell in box other than ones in that row are assigned 9, then row 4 will have no 9. Therefore no cells in the box except those in row 4 can have 9 as a candidate. The same eliminations can be made with an x-wing in column 2 & 4, row 5 & 6. If you're referring to the post by David Bryant, the technique is a variety of colouring, in which conjugate links are labeled to indicate opposite states of being. A conjugate link is one in which if one is true the other is false and if one is false the other is true. This one involves two seperate conjugate chains linked on candidate 7.

- Code: Select all
` `

*-------------------------------------------------------*

| 9 45 56 | 14 7 8 | 135 2 356 |

| 25 1 278b | 3 6 29 | 4 578B 89 |

| 3 247 2678 | 14 5 29 | 1789 678 689 |

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

| 245 8 27A | 6 3 1 | 279 57 249 |

| 24 2379a 1 | 29 8 5 | 6 37A 234 |

| 6 2359 235 | 29 4 7 | 2358 1 2358|

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

| 1 235 235 | 8 9 346| 235 346 7 |

| 8 235 4 | 7 1 36 | 235 9 2356|

| 7 6 9 | 5 2 34 | 38 348 1 |

*------------------------------------------------------*

I've labeled one chain with A-a and the other with B-b. In column 8, B & A share a group. In column 3, b & A share a group. If A is true, then neither B nor b can be true, which means row 2 will not have a 7. Therefore A is false and a must be true.

If you are referring to the 'Glassmans pan' referred to by dotdot, I have no idea what that means.

Tracy