The New Sudoku Players' Forum

[iRob]

I'm stuck on this one! Here's my progress so far:

Code: Select all

+-------+-------+-------+
| . . 5 | 8 3 2 | 6 . 1 |
| . . . | 6 . . | 8 . . |
| 1 8 6 | 9 . . | . . 2 |
+-------+-------+-------+
| 3 7 . | . 9 . | 2 . . |
| 6 . . | 5 . 7 | 1 . 3 |
| . . 1 | . 6 . | 9 . 7 |
+-------+-------+-------+
| 8 . . | . . 6 | 7 1 9 |
| . . 7 | . . 9 | . 2 . |
| 9 . 2 | 7 4 . | 5 . . |
+-------+-------+-------+


Can anyone lend a hand/technique? Thanks!

[emm]

I'm not sure exactly how far you've got, iRob, without knowing what candidates you have for the empty cells.

This puzzle has lots of examples of locked candidates = if a candidate has to be in one row or column in one box then you can eliminate it from all other cells in that row or column in the other boxes.

The candidate 3 must be in row 2 in box 1 => remove all other 3s in row 2. Also locked - the 4s in column 6 in box 2 and the 5s in row 6 in box 4.

Once you’ve got this far you’ll find a pair 8,4 hidden in box 6 => remove all other 8s and 4s from box 6 and column 8. If these terms are unfamiliar check out this site Simple Sudoku

There are more locked candidates and pairs which once you find them will crack the hardest part of the puzzle - from there it will fall apart. See how you go, but come back if you’re still stuck.

[Shazbot]

To start, look for locked candidates 4's in box 9, which will allow you to place a number in box 7. This leaves you with quite a few hidden pairs, and a single spot for a 5 in column 2, and again in row 7. That ought to get you moving.

(ah - Em beat me, but I'm not going to remove my post - I finally have enough of a handle on this that I can be helpful to SOMEONE, and I'm gonna make the most of it!)

[emm]

Hi shazbot, I think it's just you 'n me - the northern hemisphere is asleep. Next one I'll leave for you. OK!

[Karyobin]

'm not.

[emm]

OK then you can do the next one - but only if you promise you're in a fit state.

[iRob]

Ahh, thanks all! This technique of locked candidates is pretty new to me. I see it, now that you point them out to me. But... are there particular patterns to concentrate on?

I see how candidate 3 in row 2, box 1 is a "three in bed" as I've read elsewhere. But the 5s in row 6, box 4 relies on that 5 in r1c3. It's a tough pattern to "see" just in glancing.

Hmm.

[emm]

But the 5s in row 6, box 4 relies on that 5 in r1c3.

The 5s in box 4 are locked because of the 5s across the rows in box 5 & 6 - nothing to do with the 5 at r1c3.

You have to look both across the rows and down the columns to cover all bases.

[Karyobin]

I wasn't. Probably not much better now.