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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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 Posted: Wed Sep 24, 2008 6:13 am Post subject: challenging "hard" with unexpected shortcut |
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From today's paper:
| Code: |
+-----------+-----------+-----------+
| . . . | . . 1 | . . 3 |
| 7 . . | 6 . . | . 8 . |
| 8 . . | . . . | 9 . . |
+-----------+-----------+-----------+
| . . . | . 3 9 | 4 . . |
| 5 . . | 7 . 4 | . . 9 |
| . . 3 | 1 5 . | . . . |
+-----------+-----------+-----------+
| . . 1 | . . . | . . 7 |
| . 9 . | . . 5 | . . 6 |
| 4 . . | 8 . . | . . . |
+-----------+-----------+-----------+
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To print it, use this link: play online
Took me a long time to wade through nasty PMs, and of course I made a mistake. This was one of the times when I felt like using my computer for the tedious groundwork  |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Wed Sep 24, 2008 6:21 am Post subject: |
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I started over again, and found a very simple shortcut, just when things began to get nasty. When I was done with sweeping, I realized I had found a strong link (7) in r1c78, which - together with 67 in r6c78 - looked like a UR type 4.
Whatever candidates might appear in those two cells r1c78, they could never be "6". Together with the 6 in row 2, this allows to place "6" in r3c8 and the puzzle practically solves itself.
P.S.: I did use my computer afterwards to find out if there were any advanced steps required, and it is a straight "hard", although some naked quints might be difficult to spot, especially in a sea of multi-candidate PMs. |
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cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
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| Posted: Wed Sep 24, 2008 11:37 am Post subject: |
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I thought a "hard" would need no advance techniques but this one needed most of the arsenal. Notwithstanding a couple of quads, I used two xyz wings, one xy wing and two Type 4 URs <67> and <13>.
Good one - though I'm sure I over-killed it. |
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ravel
Joined: 21 Apr 2006
Posts: 536
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| Posted: Wed Sep 24, 2008 1:22 pm Post subject: |
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Nice observation, nataraj.
Without the UR you would need the hidden pair 49 in row 1, which is the hardest to spot out of the 4 hidden pairs in the grid (58 in row 7 and 67 in column 7 are straightforward, for the 13 in column 2 you need to see the locked 3 in box 1). You need the locked 49 in column 8/box 9.
Later the 67 pair is enough to solve it. |
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nataraj
Joined: 03 Aug 2007
Posts: 1048
Location: near Vienna, Austria
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| Posted: Wed Sep 24, 2008 5:39 pm Post subject: |
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| ravel wrote: | | Without the UR you would need the hidden pair ... |
I know, I know ... and since I can never ever spot hidden pairs but have to find the complementary quints (?) it is even more tedious (it means having to write REAL small )
No wonder Craig found the xyz, xy, etc. ... before the naked pairs.
In this case the "advanced" steps are definitely easier than the "basic" ones. |
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