The New Sudoku Players' Forum

[Yogi]

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UniquePr.png (15.77 KiB) Viewed 749 times

Here we have 59 in r1c27 and it's easy enough to see that r3c27 cannot BOTH be reduced to 59 only if we are to have a uniqe solution.
But how does the logic prove that NEITHER of r3c7 can be 9?

[StrmCkr]

C4R9C8b6c7 digit 1 => r3c6 <>1

Pretty easy to spot one of many fish/coloring options .(not on my cpu to post the fish logic atm)

What you ask for is uniqueness assumptive logic of a unique rectangle probably type 4 if i recall correctly

edit: yup type 4

due to the strong link in row 3 for digit 5
see elevens notes below.

[Yogi]

Thanx. It's true that fish can be found to solve this puzzle. For example the Skyscraper {1r29} => 9r7c9 stte.
I just thought it would have been easier to understand a more direct causal connection between the 59 Locked Pair and the elimination of the corresponding 9s in Row3

[Leren]

Withdrawn - eleven is right (as usual) .

Leren

[eleven]

Here we have 59 in r1c27 and it's easy enough to see that r3c27 cannot BOTH be reduced to 59 only if we are to have a uniqe solution.
But how does the logic prove that NEITHER of r3c7 can be 9?

It is called unique rectangle type 4.
You have a strong link for 5 between the UR cells in row 3, so one must be 5 and both must not be 9 to prevent the deadly pattern 5-9-5-9.

[Yogi]

Gotcha. Thanx.