The New Sudoku Players' Forum

[Pat]

Pat, yes I agree. After redoing the puzzle, using pencil marks this time, I can see that it is possible to reduce the candidates availlable on r2 to a naked double, which opens up the puzzle as you have commented.

Unfortunately, when puzzling without pencilmarks, remembering the steps taken is not the first priority and indeed it becomes quite difficult to remember.

perhaps i should have mentioned that i'm quite a slow solver and never try for speed - on the contrary, i make it a point to record my steps which certainly slows me down!

i never use "pencilmarks" as such - but i do make a note of any useful observations such as a duo or an X-wing, with the useful consequence noted (as in the example i had posted above).

slow, but that's my interest in solving SuDoku.

~ Pat

[Heuresement]

To Cathy: I was successful in completing today's Superior #33 in the Sunday Times, without any pencilmarks etc. I have been feeling pleased with myself all evening I hope that you are successful too.

Fortunately, I noticed two sets of locked candidates across the middle band in the puzzle, which revealed the location of the triples, which helped to open up the rest of the puzzle.

To Pat: I, too, like to be able to fully understand the puzzles that I do, but am often forced to complete them as quickly as possible in order to spend time with my family. However, noting your comments, and not wanting to pass on bad information to anyone else, I will check that any steps that I write down are accurate, by resolving the puzzle again. To be honest, I was unaware that there were so many people that solve without "pencilmarks", and am still pleased that I have been able to do so for the last 3 months of Fiendish ones. Hopefully now, each Sunday too.

[CathyW]

Sadly didn't have enough time to do this one without pencilmarks though I did solve it. Well done - it is very satisfying to complete a puzzle without!

BTW - what part of Cornwall are you from? My parents live in St Day near Truro.

[Heuresement]

BTW - what part of Cornwall are you from? My parents live in St Day near Truro.

We live in Falmouth which is only a few miles down from St.Day.

[tarek]

I've started a thread for posting superior level puzzles.

here is the link http://forum.enjoysudoku.com/viewtopic.php?t=3585&start=0. Great contributions from the members

If you can't get enough on a Sunday, then check it out & Hunt those triples & x-wings.

Tarek

[Pat]

I was successful in completing today's Superior #33 in the Sunday Times, without any pencilmarks etc. I have been feeling pleased with myself all evening.

Fortunately, I noticed two sets of locked candidates across the middle band in the puzzle, which revealed the location of the triples, which helped to open up the rest of the puzzle.

{ broken link -- www.timesonline.co.uk/article/0,,18209-2075701,00.html }
The Sunday Times #33 (2006.Mar.19)
seems a respectable Hard puzzle,
i did need a duo to solve it - but not a trio.

i wonder what makes it Very Hard?
(but after #31, we don't ask that question any more.)


the inviting trio in r4 is unnecessary -
r4c8 is known by Basic Elimination.

~ Pat

[Heuresement]

Pat, if I may briefly explain my original thought process that I used after inspecting the puzzle, but before I had really begun to fill in cells, it will explain why I said triples (trios) rather than doubles. Consider the middle band of this puzzle:

Code: Select all

 |---+---+---|
 |53.|4..|...|
 |..2|...|9..|
 |...|..8|.61|
 |---+---+---|


What I immediately noticed was that for the left 3x3 box, 8,6 and 1 are excluded from the bottom row, so the 8,6,1 must be the candidates for r4c3, r5c1 and r5c2 leaving the bottom three cells r6c1, r6c2 and r6c3 to have the triple candidates 4,7 and 9.

The right 3x3 box can also be populated in a similar fashion using the 5,3 and 4 in the top row of the middle band. So the top and bottom rows are known to consist of two sets of triples.

Eliminating using the digits from the rest of the puzzle allowed me to place the 8s in the middle band too (as you have remarked r4c8=8). I was then able to proceed quickly with the rest of the puzzle.

I am not claiming that this was the best technique to apply, but it was the one that I spotted first, to open up the puzzle.

I speculate that the Pappacom software ranks such as puzzles as v.hard, because triples can be applied as shown, although other tecniques can make the use of these triples redundant. Indeed that was the case with the Superior from a fortnight ago (#31).

[Bigtone53]

Exactly my breakthrough too, Heuresement. This was 20-minute job and I am both slow and loath to use pencilmarks (although I do!)

[Pat]

Same here!
I never do a thorough Basic Elimination - I'm not a computer.
Thus, my actual sequence of solving went like this:
- I noticed the r6 trio, and the r4 trio;
- saw that the r4 trio would immediately give me the r4 7,2,8 (in that order);
- and, my attention having thus been called to this particular slice of the puzzle,
I suddenly realized that the trio is unnecessary,
that r4c8 is known by Basic Elimination from the very start -
which I had earlier missed.

That's all I was saying - that the puzzle can be solved without a trio.
It's quite possible that solving with the trio may be considered easier!
( Excepting beginners who haven't learnt the trio yet. )


Later, I did need a duo to solve it -
but of course I never know if my method was the simplest,
perhaps the duo too was unnecessary??


~ Pat