The New Sudoku Players' Forum

[QiGuy]

I have tried this puzzle twice and get to the same point. Can't get any further. Can anyone help? Thx.

Code: Select all

128  7    126  4    569  3    569  68   258
249  249  3    126  8    15   7    46   245
248  5    246  26   69   7    3469 1    2348
5    24   24   3    1    6    8    7    9
6    1    9    5    7    8    34   2    34
7    3    8    9    2    4    1    5    6
134  6    145  8    35   2    45   9    7
39   89   7    16   4    15   2    368  58
234  248  245  7    356  9    456  3468 1


[QiGuy]

Sorry for the jumble of numbers -- I pasted it in from Excel and it didn't take the spacing.

[JasonLion-Admin]

I fixed up the formatting for you. The key step is to use a code tag around the fixed format text.

I see a unique rectangle.

[QiGuy]

Wow! Is it r2c4, r2c6, r8c4, r8c6? In which case r2c4 must be 2?
I've never used that before; if I've got it right, I can see that it's very effective.

[QiGuy]

No, I don't think I have identified the rectangle. May need some assistance here.

[JasonLion]

A type 4 in R35C79 on 34.

[daj95376]

There's also a pair of X-Wings present. One is very productive, the other isn't.

[QiGuy]

Is the effect of the unique rectangle, type 4, that because the 3 MUST be in r3c7 or r3c9, then the 4 can be in neither? Sorry to be thick about this, but I've not run into these before and I'm eager to pick up this technique.

[QiGuy]

Also, daj95376, point out the productive X-wing and I'll see if I can find the other.

[JasonLion]

Look at the digit 6 in rows 2 & 8.

[QiGuy]

Got the X-Wing; thanks. Still confused about the rectangle.

[ronk]

Is the effect of the unique rectangle, type 4, that because the 3 MUST be in r3c7 or r3c9, then the 4 can be in neither? Sorry to be thick about this, but I've not run into these before and I'm eager to pick up this technique.

If digit 4 is ultimately placed in neither r3c1 nor r3c3, then r35c79 contains a deadly pattern -- in this case, candidates <34> in all four UR cells. The deadly pattern cannot occur in a puzzle with a unique solution. Therefore, ultimately either r3c1=4 or r3c3=4. All digit 4 candidates that see both these cells may be eliminated.

[QiGuy]

Nice! Thanks very much -- got it!