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nov14 hard
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alanr555



Joined: 01 Aug 2005
Posts: 194
Location: Bideford Devon EX39

PostPosted: Fri Nov 18, 2005 2:48 am    Post subject: Reply with quote

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> I found this one quite straight forward in that I did not have to go
> beyond the simple solving methods. I did not have to look for any
> sets (naked or concealed).

What constitutes "simple" here?
The sets need to be identified - either explicitly or implicitly. There
are virtues in implicit identification as then one does not need to
search for them!

> It took me 64 minutes; this was beause when I do a puzzle
> labelled "Hard"; I only spend a few minutes finding a few easy
> numbers; I then go straight into writing, in every empty cell, all
> the possible candidates.

This comes back to time management.
In another post we were counselled against writing out the profiles
at too early a stage.

Is it possible to trust the grading? Some "hard" or "very hard" puzzles
do not need the candidate profiles. Others do.

I recall SamGJ posting at one time that there is a tendency for human
solversto use more complicated techniques than are necessary. I
suppose that this "over-complication" is a human trait! I attempt to solve
"medium" puzzles without pencil marks at all - whilst knowing that most
of them would be a "doddle" if such marks are used. Similarly, it is a
challenge to resist resort to more complicated procedures until as late
as possible in the solving process for any particular puzzle.

> I know this is boring and time consuming, but, (if done carefully
> without making errors) it makes looking for sets and other patterns
> much easier.

a) There is at least one site where one can request a "sweep" after
    entering a puzzle's data. This does the derivation of the profiles
    (elimination only where an intersecting row/column/region has
     the digit included - no fancy stuff!) and includes the profiles as
     superscripts (top left corner) in each cell.

    This gets rid of the tedious/boring bit but requires the user to do
    the logic bit such as identifying subsets and maintaining the profiles
    as and when additional cells are resolved.

b) Aside from (a) above, how does one ENSURE that the task is done
    "carefully without making errors"? Some advice on techniques
    would be useful. I find that I go to sleep during the process (well
    it is described as boring!) and have to restart/recheck the work.

c) Having set up the profiles (which having been set at a relatively
    early stage may have several digits in many cells), how does one
    decide where to look first (or second, third etc) in the search for
    patterns that are useful in reducing possibilities to certainties?

My own view is that using this approach is akin to the computer solver
approach. It is looking for patterns of numbers and loses the "spatial"
aspect of the puzzles. I started out with the profile inspection as the
core principle. Gradually I am awakening to the spatial checks that
can be applied - but doubt that I shall ever be as proficient in that as
our friend from Colorado.

I regard "Mandatory Pairs" as a compromise method which avoids the
tedium of candidate profiles (as numbers are recorded as and when
one finds a "pair" rather than all having to be done to gain benefit)
and also assists with the spatial aspect by recording the "intermediate"
results (rather than one having to hold such in one's memory whilst
working on the next stages in the logic).

Alan Rayner  BS23 2QT
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thesaint



Joined: 17 Nov 2005
Posts: 4
Location: Cambridgeshire

PostPosted: Fri Nov 18, 2005 3:22 pm    Post subject: The "Hard" one Reply with quote

Alan, As I have already stated on this puzzle, although not "Easy" it was not specially hard. No fancy methods were needed to solve it - not even naked pairs. From your stated intermediate position; you should have written in all the candidates in all the empty cells. You would soon see that r8 c8 only had one candidate (a 5). You would immediatly find 2 more 5s and thus hopefully progress to the end. Regards from Mr. Templar
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