End View Sudoku

For fans of Killer Sudoku, Samurai Sudoku and other variants

End View Sudoku

Postby Pyrrhon » Sat Nov 11, 2006 5:43 pm

Fill the grid with the digits 1 to 6. Each row, column and 3x3-box will have exactly one of each digit and 3 empty cells. The clues along the edges tell you which digit you can see from that vantage point.

Image
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Postby Smythe Dakota » Tue Nov 14, 2006 4:30 am

Nice puzzle -- and just the right degree of difficulty. I solved it with just singles, pairs, and some home-brew logic springing from the unusual features.

The answers came slowly, one or two at a time. That, according to one Sudoku author, is the mark of a hand-made puzzle. He expresses disdain for computer-generated puzzles, saying they tend to present only one difficult situation at the beginning, then the whole puzzle solves -WHOOSH- way too quickly.

At the risk of sounding like a broken record, this puzzle is exactly what a variant should be -- not too difficult, but involving some unusual logic. Those who like killers and those who like variants are a very different bunch.

Bill Smythe
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Postby Jean-Christophe » Tue Nov 14, 2006 11:15 am

Nice one with interesting logic. BTW I, for one, enjoy all kind of variants, incl. killer.:)

Solution:
+-------+-------+-------+
| 1 . . | 4 3 5 | . 6 2 |
| 4 6 2 | . . 1 | 5 . 3 |
| 3 5 . | 6 . 2 | . 4 1 |
+-------+-------+-------+
| . 4 6 | 2 1 . | 3 5 . |
| . 1 3 | 5 4 . | 2 . 6 |
| 5 2 . | . 6 3 | . 1 4 |
+-------+-------+-------+
| . 3 5 | 1 . 6 | 4 2 . |
| 2 . 1 | 3 5 4 | 6 . . |
| 6 . 4 | . 2 . | 1 3 5 |
+-------+-------+-------+
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Postby emm » Tue Nov 14, 2006 11:21 am

I totally agree with Bill - except for the bit at the end. (I presume you meant bunches not bunch!:) )

I too have become a fan of these variants of Pyrrhon's that require logic without 'extreme' techniques. But I also love killers many of which require just the sort of unfolding logic that makes these variants appealing.
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Symmetrical End View Sudoku

Postby Pyrrhon » Tue Nov 14, 2006 4:09 pm

Thank you for the flowers. If I'm right Bill means with killer a tough sudoku and not the variant with sum cages. This sum is also a crossover between ABC End View and Sudoku.

Symmetrical End View Sudoku

Fill the grid with the digits 1 to 6. Each row, column and 3x3-box will have exactly one of each digit and 3 empty cells. The clues along the edges tell you which digit you can see from that vantage point. If you rotate the grid 180 degrees, the empty cells will appear at the same location as they appeared without the rotation

Image
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Postby Bigtone53 » Tue Nov 14, 2006 5:16 pm

The clues along the edges tell you which digit you can see from that vantage point.


Sorry to be stupid but what does this mean? It presumably means more than the square next to the hint is the hinted number.
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Postby Pyrrhon » Tue Nov 14, 2006 5:54 pm

Next to the number there can be 1, 2 or 3 empty cells (or even none) before the number occurs.

Pyrrhon
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Postby Jean-Christophe » Tue Nov 14, 2006 5:58 pm

Maybe I missed something with the symmetrical one, but I found several solutions. Here are two solutions :
+-------+-------+-------+
| . . 1 | . 5 4 | 6 2 3 |
| 4 3 6 | . . 2 | . 1 5 |
| 2 . 5 | 6 1 3 | . 4 . |
+-------+-------+-------+
| . 2 3 | 5 4 1 | . . 6 |
| 6 5 4 | . . . | 2 3 1 |
| 1 . . | 3 2 6 | 4 5 . |
+-------+-------+-------+
| . 6 . | 2 3 5 | 1 . 4 |
| 3 4 . | 1 . . | 5 6 2 |
| 5 1 2 | 4 6 . | 3 . . |
+-------+-------+-------+

+-------+-------+-------+
| . 3 . | . 5 4 | 6 2 1 |
| 1 4 6 | . 2 3 | . . 5 |
| 2 . 5 | 6 1 . | 3 4 . |
+-------+-------+-------+
| . 2 3 | 5 . 1 | 4 . 6 |
| 6 5 . | 4 . 2 | . 1 3 |
| 4 . 1 | 3 . 6 | 2 5 . |
+-------+-------+-------+
| . 6 2 | . 3 5 | 1 . 4 |
| 3 . . | 1 4 . | 5 6 2 |
| 5 1 4 | 2 6 . | . 3 . |
+-------+-------+-------+
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Postby Pyrrhon » Tue Nov 14, 2006 8:26 pm

There was a mistake in painting the puzzle. (a misplaced 5). I've corrected it.
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Postby Ruud » Tue Nov 14, 2006 10:29 pm

Beating udosuk by a second...:D

.3..54621
146.23..5
2.561.34.
.235.14.6
65.4.2.13
4.13.625.
.62.351.4
3..14.562
51426..3.


Interesting variant (more flowers)

Special techniques that can be used:

X or Nothing

The first non-empty cell facing a vantage point can only contain that digit or must be empty. 5 other candidates can be removed.

Maximum depth

From the vantage point, the marked digit must occupy one of the 4 cells closest to that border. You can shorten that depth if the box or row already contains other empty cells.

Symmetrical emptiness

The symmetry requirement allows you to mark the opposite cell as "must be filled" or "must be empty". The center box offers an additional trick which I will not reveal at this point.

Ruud
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Postby udosuk » Tue Nov 14, 2006 11:51 pm

Ruud wrote:Beating udosuk by a second...:D

Make that a week or even a month... Don't have time for this now...:D
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Postby Smythe Dakota » Wed Nov 15, 2006 4:20 am

Bigtone53 wrote:.... what does this mean? ....

If you stand on one of the digits around the edge and look inward into the puzzle, the first thing you'll see is that digit. If you stand on an outer 5, for example, the first non-blank cell in that direction will be a 5. Thus either the first cell has a 5, or the first is blank and the second is a 5, or the first two are blank and the third is a 5, or the first three are blank and the fourth is a 5. (Can't have more than three blanks, since there are only three blanks in each row/column.)

Bill Smythe
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Postby Jean-Christophe » Wed Nov 15, 2006 6:18 am

Pyrrhon wrote:There was a mistake in painting the puzzle. (a misplaced 5). I've corrected it.


Thanks, it's OK now:)

BTW it can be played using any soft for regular sudoku, using 789 for the empty cells.

A hint :

For the central nonet/box 5, think of the implications of the symmetry and the number of empty cells : one cell must be empty.
Then some candidates are locked in 2 symmetrical cells in the central nonet/box 5 : these cells cannot be empty.
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