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Difference between revisions of "Sudoku/Methods/Advanced/Simultaneous Bivalue Nishio/Sudoku Addicts Workbook/150"

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(Created page with "==Introduction== *[http://www.sudokuwiki.org/sudoku.htm?bd=090006030004080900803090020001300009030701060200008300010070403007030600020600090 Raw puzzle]. *SW Solver: Diabolica...")
 
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==Solution==
 
==Solution==
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===Ready to run BSN===
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[[File:Addicts150-1.png|thumb|Figure 1]]
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See '''Figure 1''' on the right.
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Because I had resolved a swordfish in the book, I did so here as well before starting coloring.
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===Seed 1: Contradiction===
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[[File:Addicts150-3.png|thumb|left|Figure 2]]
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See '''Figure 2''' on the left. Seed pair is r1c5={15}. The {1} chain creates {4} in two positions in c8, therefore r1c5=5.<br><br><br><br><br><br><br><br><br><br><br><br><br><br><br>
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===Seed 2:===
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[[File:Addicts150-4.png|thumb|Figure 3]]
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See '''Figure 3''' on the right. Seed pair was r7c1={69}. With many common eliminations and confirmations, what is seen is the seed about to be confirmed as {9}, full proof of unique solution.
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==Comments==
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At no point in this process is there a "guess" as to a solution. What is done is to pick a pair for coloring, and because there may be many options, this might be considered a "guess." But it has been shown with many sudoku that the pair chosen is not critical. Rather, pairs may be more or less productive, but none are "wrong" or "errors," so this is not "trial and error." It is a systematic and fully logical examination of the consequences of two exclusive possibilities. It looks complicated, but the actual process is simple at each step. What has been missed in many descriptions of bifurcation is the interaction between the forks or "legs," as I call them.

Revision as of 23:07, 15 August 2019

Introduction

  • Raw puzzle.
  • SW Solver: Diabolical grade, overall score 225.
  • Stephens' estimated times: Improver: N/A, Expert: 414 mins, Genius: 138 mins.

Solution

Ready to run BSN

Figure 1

See Figure 1 on the right.

Because I had resolved a swordfish in the book, I did so here as well before starting coloring.

Seed 1: Contradiction

Figure 2

See Figure 2 on the left. Seed pair is r1c5={15}. The {1} chain creates {4} in two positions in c8, therefore r1c5=5.














Seed 2:

Figure 3

See Figure 3 on the right. Seed pair was r7c1={69}. With many common eliminations and confirmations, what is seen is the seed about to be confirmed as {9}, full proof of unique solution.

Comments

At no point in this process is there a "guess" as to a solution. What is done is to pick a pair for coloring, and because there may be many options, this might be considered a "guess." But it has been shown with many sudoku that the pair chosen is not critical. Rather, pairs may be more or less productive, but none are "wrong" or "errors," so this is not "trial and error." It is a systematic and fully logical examination of the consequences of two exclusive possibilities. It looks complicated, but the actual process is simple at each step. What has been missed in many descriptions of bifurcation is the interaction between the forks or "legs," as I call them.