Logic Puzzle Forums (http://www.logic-puzzles.org/forum/index.php)

 dingo170 03-30-2011 04:01 PM

Guessing?

I'm still new to this site but have come across 2 puzzles that seem to require a guess after all clues have been addressed - is this by design? If not, how can I report or question a puzzle? Is there an identifier for each puzzle that i haven't seen? Is there a contact for reporting puzzles that may not have a logical solution? <<Note - just realized URL must contain puzzle identifier>>

 rush1169 05-05-2011 04:52 PM

I have yet to find a puzzle that requires guessing. When I play, I refresh over and over until I find a very low success rate and very high average solve time and do those only. I don't think there are any that require guessing, but they for sure do require some serious thought :)

 seanandkitten 05-05-2011 11:30 PM

Guessing

Guessing is never required for the puzzles, because it would defeat the purpose. Sometimes, on the harder puzzles, it may seem that more clues are needed, but generally on those you have to combine clues. For example sometimes it says "Alan had a day off later in the week than" and sometimes it says "Alan had the day after John off." When John is not off on Wednesday, then Alan can't be off on Thursday.
Sometimes you can combine several clues, for example if Alan is off earlier than John, and John is off earlier than the person who collects butterflies, then you know that Alan does not collect butterflies, and that Alan, John, and the butterfly collector must be in that order (not necessarily consecutive).
If you come across one you can't solve, take a screen shot and email it to me at sao090020@utdallas.edu, and I can walk you through it.

Sean

 zenobia43 03-05-2012 07:26 AM

Guessing

I'm relatively new at these, and until recently, I thought that some of the tougher puzzles required guessing to see if the guess resulted in a conflict.

I actually found one where a "Of A and B, one is this and the other is that" clue led to a side effect that was identical for both choices. I thought I had found the key. Not.

When you finally get to the clues of the type indicated above, they are really a very rich source of information.

Suppose you have "Of Mary and the person who arrived on Monday, one eats Wheaties for breakfast, and the other drives a Ford."

Normally you would start by X'ing out Mary/Monday, and Wheaties/Ford, and then checking both outcomes to see if only one of them can be true.

Sometimes, both outcomes are still possible. Here is what you can do to glean more logic from the clue.

First associate Mary with the same category as the entity she is paired with. In the example given above, that would be days of the week. If there are any days X'd out other than Monday, that's a good sign.

Suppose that Mary cannot be Tuesday or Wednesday. Then you know that the left side of the proposition can only be Monday, Thursday or Friday. Go check Wheaties and Ford to see if Tuesday and Wednesday are X'd out.

Second, associate Monday (still working on the left side of the proposition) with First Names (because that is the same category as Mary in the example). If Monday has any names X'd out other than Mary, that is good.

Third, associate Wheaties with cars and repeat the procedure above.

Finally, associate Ford with breakfast cereal and repeat again.

When even this doesn't yield enough constraints to finish the puzzle, do something similar for the "ordering" clues.

The clue is usually "A arrived earlier than B" or "A arrived the day before B arrived".

If A and B aren't in the same category, associate each one with the other's category to see if an X can be placed.

Finally, there are times where the puzzle is fairly complete, but things appear to be stuck. Look for cases where there are only two open cells in two columns and the two entities are related by a clue similar to "A arrived the day before B".

There will be one overlapping day between A and B, and you know that either A or B must occupy that day. So C, D, and E cannot be the day where A and B overlap. That might get you another X which will break things loose.

When I started using the above, I started to solve the tougher ones without guessing.

If you know of something easier yet, please post. :)

If this was helpful, I know of yet one more technique, and I'll post it if there is interest (and someone hasn't posted something a lot easier).

 hayley23 03-06-2012 04:02 AM

No i get ya. the ones that have a high average time (like in the 1000 sec) does require a guess. I think that is stupid. I have seen so many times where it does NOT give you enough info. especially the ones that you dont have a single connection

 zenobia43 03-07-2012 06:05 PM

Guessing

Until lately, I thought that some of the tougher puzzles required "guess and check". I was convinced that there wasn't enough information to solve the puzzle. I didn't believe those who claimed that guessing wasn't necessary.

Now I'm a believer.

One of the toughest puzzles for me was one involving days of the week, first names, hobbies, and planets. Using all the methods of my previous post and one additional technique, I was able to solve most of the grid.

The additional technique was to check the pair-wise intersections of the categories to see if the intersection was null.

For example, if the intersection of Jupiter and astronomy across the days of the week was null (there were no open cells i.e. the intersection could not be true), then Jupiter could not be astronomy.

Even after checking all the intersections, I still couldn't finish the grid.

Then I noticed that a partial intersection was null. I noticed that Wednesday and Thursday could only be archery and astronomy, and when I combined those two I looked down into the adjacent grid and noticed that Neptune could never be true. After adding an X for Neptune in one of the rows, the rest of the puzzle was easy.

Finally, there is one last technique that appears to be very obvious to me now, but it took me a while to start using it.

Using a concrete example: If you see that Monday and Tuesday can only be Alondra or Brielle, then the other days of the week cannot be Alondra or Brielle. Pretty obvious, but the X's are being derived from the pattern in the grid rather than directly from the list of clues.

I now believe that all of the puzzles can be solved without "guess and check". There is always a logical relationship buried in the grid or clues somewhere that allows one to place another X that leads to the solution.

If you think you have found a puzzle that requires guessing, post the list of clues along with the labels for each category, and I'll take a whack at it.

 bocci 03-15-2012 02:29 AM

Guessing

Quote:
 Originally Posted by hayley23 (Post 634) No i get ya. the ones that have a high average time (like in the 1000 sec) does require a guess. I think that is stupid. I have seen so many times where it does NOT give you enough info. especially the ones that you dont have a single connection
You didn't read much beyond the title of the thread, did you?

 All times are GMT. The time now is 08:36 AM.