The following is an illustrated proof for the
Tough Sudoku of March 24, 2007.
This is a very easy puzzle, and only requires one to know one technique,
You should not need to refer to previous blog pages to understand
this proof. Links to these pages are found to the right, under Previous Entries.
This illustration, shows only the one step one may need to unlock the puzzle.
Puzzle at start
Some Unique Possibilities are available here.
Find them shown on the next illustration.
Possibility matrix at UP 27
Above find the current possibility matrix. At this point there are many steps possible.
While scanning for possible easy eliminations, I found the following situation on 2s:
Locations for 2s at UP 27
There are a few easy coloring eliminations available with the 2s. I will illustrate two of
them. One only needs to find one.
Coloring on 2s
Above, i5=2 => i7≠2 & h46≠2
i5≠2 => e5=2 => e9≠2 => h9=2 => i7≠2 & h46≠2
After making these eliminations, the puzzle is reduced to a cascade of Unique Possibilities
to the end.
Coloring on 2s alternate
Above is an alternate approach, commonly called a two string kite.
Again, the puzzle reduces to Unique Possibilities after i5≠2
Probably, this puzzle is a bit too easy for a tough! My rating system would rate this
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