The New Sudoku Players' Forum

[daj95376]

Still nobody has replied to a previous post where I asked if the forcing chain of:

r8c7=5 >r8c9=7>r4c9=2>r6c8=5>r5c7<>5

is valid. I am curious if I did that correctly.

There are many more knowledgeable about chains than myself, but I'm sure that it isn't a proper chain. Your initial assertion of r8c7=5 would result in r5c7<>5 if it were true. All you've done is find a chain that agrees with the initial assertion. A chain needs to do more than that -- unless it's a continuous Nice Loop.

Since r8c7=7 is actually true, your initial assertion turns out to be false, but your elimination turns out to be true. That qualifies as Lucky.

[Jasper32]

I didn't think it was correct. It made the correct removal but with a 50-50 chance of being correct, you are not sure if you were lucky or smart. I been called lucky my entire life and smart...let's not go there.

Seriously, Thank you for your help.

[Pat]

I was wondering if the following could be a vaid chain:

r8c7=5, r8c9=7, r4c9=2. r6c8=5 then 5 could be eliominated from r5c7

The chain is OK but, as I read it, it means that, if r8c7 = 5, r6c8 = 5 and I am not clear how the elimination follows.

hey Jasper32,

in view of your later posts i must point out that Steve R was being so polite that you may have missed the point

you listed a valid sequence of logical implications
except at the very end you added an exclusion of 5 from a cell
-- this exclusion has no logical basis