Puzzle Corner

[Black Hole]

These are too easy now...



...but for more of a challenge: what is the minimum number of inferences required, and which are they?

To be clear: an "inference" is a square not forced by the rules at the time it is filled in, but would lead to a breaking of the rules later if filled in with the other symbol. The rules are: 1. 3 O's and 3 X's in every row and column; 2. not allowed a string of 3 O's or 3 X's in any row or column. Thus: X in C3 is not an inference, because O breaks the rules immediately.

Spoiler: My solution

F2, B2

 

[EEPhil]

...but for more of a challenge: what is the minimum number of inferences required, and which are they?

I think you're probably right. After completing the puzzle with as many inferences as it took using my scatterbrain approach, I tried again. Thought I could do it in two, but then I found I was stuck and had to resort to both (ends-1) of row 1 (after the simple moves) - thus making 4. I can't see an obvious way of only one inference.

 

[Black Hole]

 

[EEPhil]

It’s a Saturday one. Third week where I managed without guessing. Is it just me or was this one easy?

 

[Black Hole]

Is it just me or was this one easy?

Sorry Phil, it was easy.

Sunday's:

 

[EEPhil]

That didn't appear too difficult either. So that's the theory about an easy one and a difficult one kyboshed. (And not koshered as the autocorrect/spellchecker wanted.)

 

[Black Hole]

Easy:



Trickier:

 

[EEPhil]

Easy:

Really? I had to go back to the trial and error method to determine where 4 and 5 went in the top row.

Trickier

I haven’t looked at this one yet.

 

[EEPhil]

Trickier:

Hmm. Just as tricky for me. After two moves on column D I got stuck. Guessed the bottom of column C and it all fell into place.

 

[prpr]

After two moves on column D I got stuck. Guessed the bottom of column C and it all fell into place.

Spoiler

D5, D4, A4, B4, E3, E1, B1, C1, C5, C4 etc.

 

[EEPhil]

Spoiler

D5, D4, A4, B4, E3, E1, B1, C1, C5, C4 etc.

Bgr! I can see the logic behind the third move now you’ve told me. Just couldn’t see it!

 

[Black Hole]

I offer this purely for ridicule:

 

[EEPhil]

I'll give it half a star at most!

 

[Black Hole]

Moderate

 

[EEPhil]

Moderate

Not on my first attempt. I'll have another go later.

 

[Black Hole]

What's not right here?

 

[EEPhil]

What's not right here?

Given that I still haven't solved yesterday's, don't ask me! I'll download the image for later.

 

[EEPhil]

Looks like that one really is trial and error. I can see no obvious start.

 

[Black Hole]

I can see no obvious start.

Not counting two 1's and three 5's that is...

Looks like that one really is trial and error.

Yes. I spent a while on the logic until I realised there is no logical solution... and the reason is that there are two solutions.

 

[Luke]

Yes. I spent a while on the logic until I realised there is no logical solution... and the reason is that there are two solutions.

Please would you post both of those. I can only see one solution and I'm not aware that I used trial and error, but perhaps I made a mistake somewhere and got lucky.