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.
Last edited by zenobia43; 03-08-2012 at 04:58 AM.