I would first note that Different Neighbours is a Vladimir original type (as far as I know) and when he introduced the type there were few questions on how to solve it - he explained it here - http://www.forsmarts.com/forum/viewtopic.php?id=33

Without revealing much about the actual puzzle (since the test is running), I think your approach that placing letters instead of digits in empty cells (Placeholders) is definitely one strategy to be used.

Edited by debmohanty 2012-01-24 8:50 AM

Yes even I had a lot of trouble in solving this puzzle, I thought of posting about this once the contest ends.
I couldn't figure out from where to start but I became stubborn about solving this and finally managed to solve :)

Regards,
Ravi

Many thanks for the reference. It was good to have another example so I could get up to speed.

The puzzle mechanic is an interesting change of pace from other puzzle types I've gotten used to.