The New Sudoku Players' Forum

[adrianzr]

pleas help with this puzzle, ive read all techniques and cant figure out this one, im really stuck, been trying for hours, y saw an x wing with 3 and used it to fill in a number, con cant go on...

7*8 *3* **9
*** *2* **8
24* 7*8 *51
43* 8*2 **5
*8* *** *1*
6** 5*7 8*3
19* 674 *82
*7* *8* ***
8** *5* **7

thank you very much !!!!
im really desperate!

[masb]

Here are some hints from http://www.axcis.com.au/numbler:

Code: Select all

Pair Box @ r7c3 r8c1> r8c3x3 r8c3x5 r9c3x3
Box Column @ 2> r5c4x4
Column Box @ 2> r2c1x5 r2c3x5
Quad Row r5c1=5 r5c3x9 r5c7x4 r5c7x6 r5c7x9

It is staighforward from there. In the above "x" means remove pencil candidates and "=" means set value. The first step is the "35" pair in box 7 which means 3 or 5 cannot go elsewhere in this box 7. You can see this visually in the Numbler program.

[Shazbot]

From the full list of candidates

Code: Select all

 *-----------------------------------------------------------------------*
 | 7      156    8       | 14      3       156     | 246     246     9   |
 | 359    156    13569   | 149     2       1569    | 3467    3467    8   |
 | 2      4      369     | 7       69      8       | 36      5       1   |
 |-----------------------+-------------------------+---------------------|
 | 4      3      179     | 8       169     2       | 679     679     5   |
 | 59     8      2579    | 349     469     369     | 24679   1       46  |
 | 6      12     129     | 5       149     7       | 8       249     3   |
 |-----------------------+-------------------------+---------------------|
 | 1      9      35      | 6       7       4       | 35      8       2   |
 | 35     7      23456   | 1239    8       139     | 134569  3469    46  |
 | 8      26     2346    | 1239    5       139     | 13469   3469    7   |
 *-----------------------------------------------------------------------*


A naked quad of 3469 in row 5 will allow you to place your next number, and a bit later you'll end up with a naked pair in box 3

[stuartn]

Another way - the 5's in C2 are in one block only - so you can make some deletions in that block - then there's a hidden pair in R5 which'll allow some more deletions and it all falls apart after that (as they say)

I'm sure there's many more ways to start on your grid - it just depends on what you look for first.

stuartn

[Tom Sawyerer]

y saw an x wing with 3 and used it to fill in a number,

i really dont get it, what u mean by those above sentence??

[adrianzr]

ok, i understood the quad in row 5, and that makes me take out 9 as candidate in r5c1, which makes me fill in a 5. and from there its pretty easy.... the thing i dont get is the hidden pair in row 5, i dont see any...
the xwing i was talking about was number 3 in row 3 and 7, which helped me fill in number 3 in box 4....
thanks you very much for your help, i will have abetter eye now to see quads..... are they vary common?? they are hard to spot when doing puzzles in pencil an paper....
with your experience is this puzzle hard or very hard ??

[emm]

Pappocom rates this puzzle as Hard – the naked quad is the most difficult step, the Xwing is actually not required although it’s more fun to find it than just picking off singles alone.

Naked quads aren’t all that difficult to spot when you're looking for them - it’s the hidden anythings that are tricky. Even stuartn’s hidden pair 7, 2 in row 5 is pretty elusive!

[Shazbot]

I find all patterns are hard to spot when you're just learning the technique. First I struggled with locked candidates. Then when I'd done enough puzzles with them and got tired of them (still not GOOD at them) I started learning about xwings. Suddenly, locked candidates became easier to find. Now I'm polishing up on swordfish and colouring, and I find xwings are easier to spot. It's just a matter of knowing what techniques are available and looking for puzzles that use them so you can hone your skills. There have been a good number of naked quads in puzzles I've done (I'm on Pappocom hard and Angus J's extreme levels now) but I usually don't see them 'cause I'm looking for the other patterns. And I'm lousy at almost ANYTHING hidden!

[adrianzr]

wow thats great information... but shouldnt you fins the nakes quad on row 5 first to fina the hidden pair 7 2 then? how can you spot de hidden pair before the quad??

[adrianzr]

im sorry, i get it know, forget what i said. im really thankfull to you guys, youve helped me a lot, if i hope not to get stuck in another puzzle.... yeah right! see ya!