Solving wapati's grids by guessing

Frank

Hallo to everybody,
probably I cannot participate to this forum because I'm a T&E sudoku solver.
Nevertheless, confrontation of different ways on solving wapati's truly interesting grids could be useful and suitable for some discussions.
So, I ask the Site Administrator the authorization to enter in this forum.
Thanks

Ruud · Site Admin

we're very open-minded here. go ahead. Smile

Ruud
_________________
Meet me at sudocue.net

Frank · Posted: Thu Jan 31, 2008 10:51 am Post subject:

Frank · Posted: Thu Jan 31, 2008 11:06 am Post subject:

As a matter of principle, any sudoku puzzle is solved following the method suitable to the solver. Any way is good to reach the target! But inside a specific zone, the choice of the solution method is commonly seen as unclever or unelegant.
I'm referring to grids, like wapati's, which cover the zone from puzzles solved by logic to the ones solved by guessing (T&E).
In this forum are shown a lot of techniques to overcome, whereit's possible, the T&R solution, assimilated perhaps to a sort of brute force applied by hand, not via computer program, I mean.
Sometimes, and wapati's puzzles are a good field of investigation, the solution can be reached after few trials, appropriately chosen, of course!
For example, we examine now the following grid:

Frank · Posted: Thu Jan 31, 2008 11:18 am Post subject:

Frank · Posted: Thu Jan 31, 2008 11:44 am Post subject:

Frank · Posted: Thu Jan 31, 2008 11:49 am Post subject:

Post n.3 repeated! This should be my post n.6.

Frank · Posted: Thu Jan 31, 2008 4:32 pm Post subject:

Now everything is normalized, I've no troubles to enter my posts, I mean.
So, my next proposal is wapati's grid of Jan.29,2008, that is the following one:

Frank · Posted: Thu Jan 31, 2008 5:57 pm Post subject:

Frank · Posted: Fri Feb 01, 2008 8:50 am Post subject:

This is the puzzle published by wapati a couple of days ago in his forum section.
See the URL below for my solution, carried out by using pencil&rubber, as usual. Some remarks to describe the symbols: cells marked with left-top corner come from logic solution, while the ones (only one in this grid) circled are referred to a double trial: if in the tree the initial tentative fails, so the second is definitive and other cells (unmarked) are filled consequently.

http://img30.picoodle.com/img/img30/4/2/1/f_wap30janm_bb1dde2.jpg

wapati · Posted: Sat Feb 02, 2008 6:06 pm Post subject:

I agree that everyone should use the methods that they prefer.

I don't expect that many people prefer to guess.

I have read that it is the fastest method, when you guess correctly. Smile

Frank · Posted: Sat Feb 02, 2008 7:24 pm Post subject:

Frank · Posted: Sun Feb 03, 2008 1:39 pm Post subject:

An empiric way to choose the initial on/off cell is to select it from a column of different blocks, namely 5 and 8 in the grid of the following link

http://img26.picoodle.com/img/img26/4/2/3/f_wap01febm_64b1a4c.jpg

Frank · Posted: Mon Feb 04, 2008 5:23 pm Post subject:

Now I want to present a typical example of a grid where the human mind prevails on brute force.
Most sudoku solvers commonly think, erroneously from my point of view, that guessing is synomym (equal) to brute force. The mind of man is tremendously slower than a computer machine but surely clever.
In this wapati's grid
http://img02.picoodle.com/img/img02/4/2/4/f_wap02febm_9be8f67.jpg
the first tentative (6 in E1) has been quickly abandoned because the procedure didn't free further cells; next choice (7 in G4) as first tree goes to the target throughout two more bifurcations.

Frank · Posted: Tue Feb 05, 2008 11:29 am Post subject: