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 Post subject: Regular Samurai #24
PostPosted: Mon Oct 06, 2008 12:09 am 
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Regular Samurai #24A (Apprentice)
Rating based on required solving techniques:  Very Hard

Image
24A Line Format:
Code:
....5......8...153.4.8.9.....7...3.53...1......1...4.7.7.6.3....3........1.2.7...
.15...4.......6..1.9..1.3.....9.2.7...4..1.3.6.8..7......2........47...........95
.....2........9........1.......7.......4..1.2295..........8.................2....
.....5...6.9......1...69......4..27...4....9..2.751...3.6.........53...8.7......6
...6....5.....1.4......9..61...8.......32.6...56...8......94.3..3....5..5.9......


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 Post subject: Re: Regular Samurai #24
PostPosted: Mon Oct 06, 2008 5:54 pm 
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Hmmm. . . Is the picture in the middle a hint? ;)


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 Post subject: Re: Regular Samurai #24
PostPosted: Mon Oct 06, 2008 8:23 pm 
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enxio27 wrote:
Hmmm. . . Is the picture in the middle a hint? ;)
It is more than that .... it is a double hint :twisted:

BTW, I couldn't find any better pictures :(

tarek


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 Post subject: Re: Regular Samurai #24
PostPosted: Tue Oct 07, 2008 12:30 pm 
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tarek wrote:
BTW, I couldn't find any better pictures :(
Try googling for "X-Wing" and select images. 8-)

Image

Image

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 Post subject: Re: Regular Samurai #24
PostPosted: Tue Oct 07, 2008 6:59 pm 
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Thanks Børge :applause:

tarek


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 Post subject: Re: Regular Samurai #24
PostPosted: Wed Oct 08, 2008 4:50 pm 
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Tarek,

Thanks for an enjoyable and IMHO easier puzzle than your last one.

Here a mini-mini Walktrough:
Hidden Text:
The nice thing about this puzzle is that it as far as I can figure out actually requires two X-Wings.
I played around a bit to see if I could substitute the two X-Wings with another single advanced technique, but without success.

When the first X-Wing is needed 310 out of 369 cells are solved, i.e. 84% of the puzzle is solved.

X-Wing on 8 in g5:r27c39 (green cells).

Image

After the eliminations from the first X-Wing have been done (pink cells), the only other elimination before the second X-Wing is a Hidden Single 8 in g5:r5c2 (blue cell).

X-Wing on 4 in g5:r49c27 (green cells).

Image

After the eliminations from the second X-Wing have been done (pink cells), the Samurai solves with N/H-Singles, starting with a Hidden Single 9 in g5:r1c7 (blue cell).

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Last edited by Børge on Sat Mar 21, 2009 3:54 pm, edited 1 time in total.

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 Post subject: Re: Regular Samurai #24
PostPosted: Wed Oct 08, 2008 7:36 pm 
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Børge wrote:
Tarek,

Thanks for an enjoyable and IMHO easier puzzle than your last one.

Here a mini-mini Walktrough:
.
.
.
Thanks & well done, I agree that last week's puzzle is more difficult by the virtue of having very little revealed at the time the x-wing arrived ....

Your path agrees with what I had. Here is the solver's path (including the redundant ones) when arriving at what you mentioned
Hidden Text:
1 in g5r6c5 is a Naked single
[g5r6c4][g5r89c5]<>1
18 is a hidden double in g5c4
[g5r8c4]<>7 [g5r9c4]<>7
7 forms an intersection in g5b8/g5c5
[g5r23c5]<>7
8 forms an x-wing in g5r27/g5c39
[g3r9c9][g5r58c3][g5r89c9]<>8
8 in g5r5c2 is a hidden single in more than one sector
[g5r9c2]<>8
4 forms an x-wing in g5c27/g5r49
[g5r4c49][g5r9c9]<>4
4 in g5r6c4 is a hidden single in more than one sector
[g5r6c9]<>4
tarek


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 Post subject: Re: Regular Samurai #24
PostPosted: Thu Oct 09, 2008 1:52 pm 
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tarek wrote:
Børge wrote:
Tarek, Thanks for an enjoyable and IMHO easier puzzle than your last one.
Thanks & well done, I agree that last week's puzzle is more difficult by the virtue of having very little revealed at the time the x-wing arrived ....
Just for the record and to avoid any misunderstandings:
I personally prefer the somewhat more difficult puzzles, like Regular Samurai #22.


I am a bit puzzled by your solver's path after the second X-Wing which yields the eliminations [g5r4c49][g5r9c9]<>4
After the eliminations from the second X-Wing have been done, IMHO the next most obvious step is:
Naked Single 9 in g5:r4c4
and not Hidden Single 4 in g5:r6c4

My view may be tainted by the fact that when solving a Sudoku using my personal helper (NOT SOLVER) I normally have "Auto-Replace naked singles with solution" turned on. I find it tiresome having to manually convert Naked Singles to solutions.

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 Post subject: Re: Regular Samurai #24
PostPosted: Thu Oct 09, 2008 6:15 pm 
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I said it before,

If you solve with Pencilmarks then it is obvious that Naked singles are easier to spot than Hidden singles.

If you are solving without pencilmarks, Then hidden singles are the easiest to spot. IMO the Apprentice level is the limit to solving without pencilmarks.

It is all up to personal opinions.

Here the solver's path if using Naked singles prior to Hidden singles
Hidden Text:
4 in g4r9c6 is a Naked single
7 in g4r7c5 is a hidden single in more than one sector
18 is a hidden double in g5c4
[g5r8c4]<>7 [g5r9c4]<>7
7 forms an intersection in g5b8/g5c5
[g5r23c5]<>7
8 forms an x-wing in g5r27/g5c39
[g3r9c9][g5r58c3][g5r89c9]<>8
8 in g5r5c2 is a hidden single in more than one sector
[g5r9c2]<>8
4 forms an x-wing in g5c27/g5r49
[g5r4c49][g5r9c9]<>4
9 in g5r4c4 is a Naked single
[g5r4c79][g5r6c4]<>9
4 in g5r6c4 is a Naked single
[g5r6c9]<>4
9 in g5r1c7 is a hidden single for g5c7

BTW, I can confirm that both x-wings are needed in that order. The 2nd x-wing is formed when the hidden single in g5r5c2 is uncovered.

tarek


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