dailysudoku.com

[keith]

There is an X-wing in the starting position. You do not need pencil marks to find it.

OK, I admit the X-wing is not "required" to solve the puzzle, but I had great fun finding it.

Keith

[Marty R.]

[orly]

I am here with this puzzle:

[David Bryant]

Hi, Orly! Welcome to the forum.

All you need to crack this puzzle is to find a few hidden pairs.

First, look carefully at column 3, and at row 7. You can see the pair {2, 6} already entered in both. Now look at the bottom left 3x3 box (box 7). Because of the way column 3 and row 7 intersect that box, it is evident that the pair {2, 6} must lie in r8c2 & r9c1 ... there are no other cells in which either of those values can possibly be placed.

OK, that was just for warmup. Here's a clue that will get you going again.

Look at the bottom left 3x3 box. The values {3, 8} are already entered there. Then look at row 5, where you will see {3, 8} once again. So there are three cells in column 3 (r5c3, r7c3, and r8c3) that cannot possibly contain either "3" or "8", implying that the hidden pair {3, 8} must lie in r1c3 & r6c3.

(Working from the diagram you posted, you can also spot this by observing the triplet of values {1, 4, 5} in r5c3, r7c3, and r8c3. I think the "hidden pairs" are usually easier to spot without the candidate lists, but either approach works.)

Anyway, with the candidates for r1c3 reduced to {3, 8} you will notice that r1c6 = 1 (unique horizontal), and you should be able to make more progress from there.

Happy sudokuing! dcb

[mazin]

[Marty R.]