Search found 86 matches

by David Bryant
Mon Oct 02, 2006 5:10 pm
Forum: Solving Guide & Glossary
Topic: Almost Locked Sets
Replies: 1
Views: 4774

Almost Locked Sets

I'm still trying to understand the "XZ rule" thoroughly. An almost locked set consists of N cells with exactly N+1 candidates. So I was working the "nightmare" puzzle for Monday, 2 October, 2006. Some fairly basic stuff got me to this point, where I applied a "Double Implica...
by David Bryant
Sat Sep 23, 2006 1:34 am
Forum: Puzzles
Topic: A "zen" sudoku
Replies: 0
Views: 2941

A "zen" sudoku

6.2.5.... .....4.3. ......... 43...8... .1....2.. ......7.. 5..27.... .......81 ...6..... This is from Gordon Royle's collection of 17-clue sudoku puzzles. When I run SudoCue (v1.5.1.3) on it, the program reports 13 instances of "table conflict" before it starts to make any real headway w...
by David Bryant
Sat Sep 16, 2006 10:19 pm
Forum: Daily Sudoku Nightmare & Archive
Topic: n00bs & daily nightmare sudokus (Sept. 15th)
Replies: 10
Views: 5034

Guess if you want to

... I shalt not guess numbers anymore. Hi again, Tomi! There's nothing "wrong" with guessing numbers. Any time you have reduced the number of possibilities in a single cell to two you can of course make a guess, with a 50% chance of being right. On a very tough puzzle, that may in fact be...
by David Bryant
Fri Sep 15, 2006 10:31 pm
Forum: Daily Sudoku Nightmare & Archive
Topic: n00bs & daily nightmare sudokus (Sept. 15th)
Replies: 10
Views: 5034

Maybe we can reconstruct it ...

Hello again, Tomi! I looked at your picture, but couldn't really make much sense out of it. So I thought I'd take a slightly different tack. I started the puzzle from the beginning and applied all the "elementary" techniques that you described. After a bit I get to this point. *-----------...
by David Bryant
Fri Sep 15, 2006 12:15 pm
Forum: Daily Sudoku Nightmare & Archive
Topic: n00bs & daily nightmare sudokus (Sept. 15th)
Replies: 10
Views: 5034

Try some of these

Hello, Tomi.

Try this one, and this one. After you've whizzed through those two, you might try this one. dcb :)
by David Bryant
Tue Sep 12, 2006 10:44 pm
Forum: Solving Techniques & Tips
Topic: Coloured Chains
Replies: 3
Views: 5773

Same deduction, different track

Hi, Ron! I used to talk to Laura a lot on this forum, but she sort of disappeared about last April, or May. Maybe she'll be back when winter rolls around in Sweden again. :) I never tried to use her "colored chains" technique (in the form she describes it), because it just seems too comple...
by David Bryant
Mon Sep 11, 2006 12:47 am
Forum: Daily Sudoku Nightmare & Archive
Topic: Sept 4 Nightmare
Replies: 4
Views: 2925

"Double-Implication Chains"

Hi, Ron! I'm probably not careful enough with my terminology. I think of a double-implication chain as being one of two things. A. A set of two chains of inference that can be drawn by considering each of two possibilities in a "base" cell. Usually the "base" cell can only take o...
by David Bryant
Thu Sep 07, 2006 3:26 pm
Forum: Daily Sudoku Nightmare & Archive
Topic: Mystery theme week
Replies: 2
Views: 2246

Mystery theme week

Ruud wrote:If you know what the theme for the week [09/05/06 - 09/11/06] is, tell us ...
At this point I'm still just guessing, but I'd say it's either short range Nishio or double-implication chains (aka "Empty Rectangles" and "XY Chains"). dcb :)
by David Bryant
Wed Sep 06, 2006 2:24 am
Forum: Daily Sudoku Nightmare & Archive
Topic: Sept 4 Nightmare
Replies: 4
Views: 2925

A "DIC" solution

Hi, Ron! I had a lot of fun with the "ALS" week. I'm still trying to understand how to spot the useful "ALS"s in a puzzle. I was able to solve all seven of the puzzles by using "double-implication chains", which I think are in many cases the same thing as "almost l...
by David Bryant
Thu Aug 17, 2006 10:45 pm
Forum: Solving Techniques & Tips
Topic: 27 Jan 2006 Nightmare
Replies: 5
Views: 14149

Astute observation

That's an astute observation, Ron. I'm not too good with names for some of these newer "techniques" -- I tend to rely on logic & first principles. Thanks for pointing out that this is an "XYZ-Wing" pattern. Maybe we can get Ruud to update the solving guide. Here's an example ...
by David Bryant
Mon Aug 14, 2006 9:40 pm
Forum: Puzzles
Topic: Another "pearl" of a puzzle
Replies: 0
Views: 2916

Another "pearl" of a puzzle

Hi, all! Since Ruud is posting "pearls" on the nightmare page this week, it seems like a good time to introduce another "pearl" from my friend Andrei's collection. *-----------* |...|.1.|78.| |5..|..9|...| |...|...|.4.| |---+---+---| |.26|...|...| |...|6..|..3| |.74|.8.|...| |---...
by David Bryant
Sun Aug 13, 2006 4:41 pm
Forum: Daily Sudoku Nightmare & Archive
Topic: Solving the Nightmare . . .
Replies: 2
Views: 2494

Here's a "forcing chain" solution

Hi, Pepi! Here's another way to solve the puzzle from the position Ruud posted. .---------------.---------------.---------------. | 1249 12 6 | 7 1489 1249| 35 48 35 | | 49* 8 5 | 39 6 349 | 7 1 2 | | 1247 3 47 | 128 148 5 | 6 48 9 | :---------------+---------------+---------------: ...
by David Bryant
Wed Jul 26, 2006 12:54 am
Forum: Daily Sudoku Nightmare & Archive
Topic: Fishing expedition ended, but keep your rods ready
Replies: 1
Views: 2185

July 25 Nightmare

Hi, Ruud! I really enjoyed today's puzzle, so I thought I would comment on it. I know you said that SudoCue doesn't employ double-implication chains. But I think it does use a couple of special types of DIC -- the XY-Wing in previous versions, and the "APE" in the versions you released rec...
by David Bryant
Tue Jul 18, 2006 12:04 am
Forum: Daily Sudoku Nightmare & Archive
Topic: July 17 -- is this a fish?
Replies: 2
Views: 2351

July 17 -- is this a fish?

After doing the more or less usual stuff I arrived at this position. 35 45 9 2 47+ 6 37- 1 8 34 7 18 19 5 148 39 6 2 28 126 1268 179 3 1789 4 79+ 5 6 29 27- 3 1 5 79+ 8 4 1 3 4 6 8 79+ 2 5 79- 578 59 578 4 79 2 6 3 1 9 146 3 5 2 17 8 47 67+ 47 8 17* 179+ 6 13479 5 2 379* 257 2456 2567 8 479 37 1 479...
by David Bryant
Fri Jul 14, 2006 4:07 pm
Forum: Daily Sudoku Nightmare & Archive
Topic: Where are the BUGs?
Replies: 3
Views: 2602

Relying on "uniquity"

Thanks for the explanation, Ruud. I went back through some of the earlier puzzles and managed to work a couple of those down to a BUG + 1 pattern by relying heavily on the "uniqueness" of each solution. That probably explains my problem -- like Chuck B, I usually try to avoid making that a...