The New Sudoku Players' Forum

[Arajmahad]

howdy folks. i am having a hell of a time with this puzzle. it's from the iPhone Finger Arts app and my first foray into the 'expert' level. i can do the 'hard' level ones, no problem, but as soon as i try the expert one, i get stumped. i've been reading up about x-wings and Swordfishes and Skyscrapers, but i can't seem to find any of those in this puzzle. maybe i've just spent too much time staring at it and am missing what is right before my eyes, so if someone out there could give me a push in the right direction, that would be sweet. i'm not looking for someone to solve it for me, or to give me a number that would kickstart the solving, but rather inform me if i have made any mistakes with my pencil marks and if not, then maybe which technique to use. if anyone out there would do me that solid, it would be much appreciated. either way though, thanks for reading.
here's the puzzle:

Code: Select all

*--------------------------------------------------------------------------*
I    25    2456      7     I    48    12    1468    I    9    236    35    I
I    8     24569     2469  I    34    23    46      I    56   1      7     I
I    1     3         26    I    5     9     7       I    8    26     4     I
I--------------------------------------------------------------------------I
I    6     1         5     I    7     4     9       I    3    8      2     I
I    279   279       29    I    6     8     3       I    4    5      1     I
I    4     8         3     I    2     15    15      I    7    9      6     I
I--------------------------------------------------------------------------I
I    579   45679     4689  I    1     357   2       I    56   346    3589  I
I    3     245679    24689 I    489   57    458     I    1    46     589   I
I    59    459       1     I    3489  6     458     I    2    7      3589  I
*--------------------------------------------------------------------------*

[SteveG48]

You have a 2-string kite on 6's that will give you an elimination at r7c3.

Unfortunately, that won't get you far. This is a pretty difficult puzzle. If you're just getting into swordfish and skyscrapers, you're going to have tough sledding with this one.

You might want to download a free program called Hodoku. It has a built-in solver (which, of course, you can ignore while solving yourself), and a huge set of solution techniques, which it can use to give you hints. It also rates puzzles on difficulty so that you know when you're in over you head (often, for me!).

[Arajmahad]

sweeeeet! thanks man. yeah, it's only a small move, but it's still a move, so it's more progress than i've made in hours. thanks again

[Leren]

Code: Select all

*-----------------------------------------------------------------------*
| 25     2456   7       | 48    a12     1468    | 9     e36-2   35      |
| 8      24569  2469    | 34    b23     46      | 56     1      7       |
| 1      3      26      | 5      9      7       | 8      26     4       |
|-----------------------+-----------------------+-----------------------|
| 6      1      5       | 7      4      9       | 3      8      2       |
| 279    279    29      | 6      8      3       | 4      5      1       |
| 4      8      3       | 2      15     15      | 7      9      6       |
|-----------------------+-----------------------+-----------------------|
| 579    45679  489     | 1     c357    2       | 56    d346    3589    |
| 3      245679 24689   | 489    57     458     | 1      46     589     |
| 59     459    1       | 3489   6      458     | 2      7      3589    |
*-----------------------------------------------------------------------*

If you were happy with the Kite, the following chain will make further progress, and solve a cell (but not the whole puzzle).

(2) r1c5 = (2-3) r2c5= r7c5 - r7c8 = (3) r1c8 => - 2 r1c8.

What the chain shows is that if you assume r1c5 is not 2 then, following the cells a-b-c-d-e you can deduce that r1c8 is 3. On the other hand if r1c5 is 2 r1c8 is obviously not 2.

Either way, r1c8 is not 2 and can be eliminated there, and you'll find that there is only one 2 left in Column 8. That should make you happy.

Leren

[SteveG48]

Also look for a W-wing.

[Leren]

Also look for a W-wing.

Hi Steve, I was limiting my hints to moves that solve a cell, otherwise the solution may be too long.

Leren

[SteveG48]

Good plan!