Moderate puzzle for a beginner...

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Moderate puzzle for a beginner...

Postby cwgannon » Sat Mar 04, 2006 8:42 pm

It began as:

Code: Select all
. . . | . 1 8 | 6 9 .
. . 5 | 7 . . | . . .
. 9 . | . . . | . . .
------+-------+------
4 . 6 | 1 . . | . 3 .
. . . | 2 . 6 | . . .
. 8 . | . . 9 | 7 . 2
------+-------+------
. . . | 8 . . | . 7 .
. . . | . . 7 | 5 . .
. 5 3 | 4 2 . | . . .


and has come to:

Code: Select all
23  347 247 | 5 1 8 | 6  9   47
168 16  5   | 7 9 4 | 3  2   18
18  9   478 | 6 3 2 | 14 145 14578
------------+-------+--------------
4   2   6   | 1 7 5 | 8  3   9
39  37  79  | 2 8 6 | 14 145 145
5   8   1   | 3 4 9 | 7  6   2
------------+-------+--------------
169 146 49  | 8 5 3 | 2  7   14
28  14  28  | 9 6 7 | 5  14  3
7   5   3   | 4 2 1 | 9  8   6



It's really quite possible that I've already made a mistake, but if I haven't, could somebody please point me in the right direction? I'm looking more to understand how to progress from here, rather than just how to fill in the numbers.

Thanks.
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Postby vidarino » Sat Mar 04, 2006 8:47 pm

It looks good so far.:)

You have a "naked triple" of 146 in column 2 (16, 146 and 14). This means you can eliminate a 4 in the top row. Then, look closely at the remaining 4s in the top box.:)

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Postby tarek » Sat Mar 04, 2006 8:57 pm

hi cwgannon & vidar,

you can also achievethe same result with the triple if you look for a hidden double in column 2......


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Postby cwgannon » Sat Mar 04, 2006 9:08 pm

I hope I don't come off as an idiot, but here's where the suggestions thus far have gotten me:

Code: Select all
23  37  247 | 5 1 8 | 6  9   47
168 16  5   | 7 9 4 | 3  2   18
18  9   47  | 6 3 2 | 14 145 14578
------------+-------+--------------
4   2   6   | 1 7 5 | 8  3   9
39  37  79  | 2 8 6 | 14 145 145
5   8   1   | 3 4 9 | 7  6   2
------------+-------+--------------
169 146 49  | 8 5 3 | 2  7   14
28  14  28  | 9 6 7 | 5  14  3
7   5   3   | 4 2 1 | 9  8   6


I'm not seeing anything that can be done with the 7's in the top row. What am I missing?

And thanks, already, for the help.
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Postby tarek » Sat Mar 04, 2006 9:29 pm

if you look at column 2

All the 4s are in box 7

As Column 2 must have a 4, you can safely eliminate other 4s in box 7, here we haveonly one elimination r7c3

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Postby tarek » Sat Mar 04, 2006 9:38 pm

Anyway,

i just noticed the original puzzle, I don't think it's moderate at all..

on the contrary, It is extremely difficult to solve by newspaper standardsespecially when there are multiple solutions..................

I'm curious, how did you make some of the elimination along the way cwgannon ???

Or could you check the starting grid again........

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Postby tarek » Sat Mar 04, 2006 9:45 pm

Don't worry,

From your pencilmarks...

r3c6 must have been 2 & was dropped out....


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Postby cwgannon » Sat Mar 04, 2006 10:34 pm

tarek wrote:if you look at column 2

All the 4s are in box 7

As Column 2 must have a 4, you can safely eliminate other 4s in box 7, here we haveonly one elimination r7c3

Tarek


That hint was all it took for me to solve the rest. I just wish I'd spotted it earlier myself.

As it turns out, this puzzle was actually rated as "Hard. Like Diamonds." by the Daily Cardinal in Madison. I figured I'd just label it as a moderate one, as it seems to be compared to some of those I've seen here.

Thanks again for the help. I appreciate it.
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Moderate puzzle for a beginner

Postby Cec » Sun Mar 05, 2006 1:22 am

tarek wrote:"..you can also achieve the same result with the triple if you look for a hidden double in column 2...."

Adding to your correct comment, when four clues ('given' numbers) appear, as in this case, in a unit (row, column or box) and a naked triple exists in that unit, then after eliminating these three candidates if existing in other cells of that unit, the remaining candidates in that unit will always form a naked pair .

I normally find it "easier" to spot naked triples than hidden pairs but that's just me. You are correct but thought I'd throw this in.

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Re: Moderate puzzle for a beginner

Postby ronk » Sun Mar 05, 2006 2:33 am

cecbevwr wrote:I normally find it "easier" to spot naked triples than hidden pairs but that's just me.

I find it easier to even spot naked quads than a hidden pair, so I certainly don't think it's "just you".

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Postby QBasicMac » Sun Mar 05, 2006 4:56 am

After removing 4 in r1c2 because of the hidden pair 37 in col 2, the locked candidate 4 in r1c3 f3c3 eliminate the 4 in r7c3.

Nothing but singles after that.

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Postby ronk » Sun Mar 05, 2006 5:24 am

Looking at the wrong grid, so comment deleted. Sorry, Ron
Last edited by ronk on Sun Mar 05, 2006 6:08 am, edited 1 time in total.
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Postby Myth Jellies » Sun Mar 05, 2006 8:06 am

Code: Select all
23  347 247 | 5 1 8 | 6  9   47
168 16  5   | 7 9 4 | 3  2   18
18  9   478 | 6 3 2 |*14*145*145+78
------------+-------+--------------
4   2   6   | 1 7 5 | 8  3   9
39  37  79  | 2 8 6 |*14*145*145
5   8   1   | 3 4 9 | 7  6   2
------------+-------+--------------
169 146 49  | 8 5 3 | 2  7   14
28  14  28  | 9 6 7 | 5  14  3
7   5   3   | 4 2 1 | 9  8   6

:DYou may think this is funny, but the first thing I saw when looking at this grid was the very obvious MUG formed by the 145 in the starred cells. This forces r3c9 = 78 which solved the 5's. It didn't exactly crack the puzzle, but it did get rid of some clutter.
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Postby MCC » Sun Mar 05, 2006 12:34 pm

Code: Select all
23  347 247 | 5 1 8 | 6  9   47
168 16  5   | 7 9 4 | 3  2   18
18  9   478 | 6 3 2 | 14 145*145*+78
------------+-------+--------------
4   2   6   | 1 7 5 | 8  3   9
39  37  79  | 2 8 6 | 14 145*145*
5   8   1   | 3 4 9 | 7  6   2
------------+-------+--------------
169 146 49  | 8 5 3 | 2  7   14
28  14  28  | 9 6 7 | 5  14  3
7   5   3   | 4 2 1 | 9  8   6

In a similar vein to Myth Jellies I saw the uniqueness rectangle of 145's which implied that r3c9=78.

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Postby ronk » Sun Mar 05, 2006 1:09 pm

MCC wrote:In a similar vein to Myth Jellies I saw the uniqueness rectangle of 145's which implied that r3c9=78.

I don't believe that's a valid deduction, since ...
Code: Select all
1    4

5    1

... is one of several possible outcomes not containing 78.

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