Place one of the four letters A, B, C or D in each of the blue-coloured cells. No letter can be horizontally or vertically adjacent to itself. The yellow-coloured tables above and to the left of the grid indicate how many times each letter appears in that column or row.

This is an extended version of ABCD.

				A	3	2	0	2	2	2	0	3	1
				B	2	1	3	0	0	1	3	0	2
				C	1	2	1	3	2	3	1	2	1
	A	B	C	D	0	1	2	1	2	0	2	1	2
	2	0	4	3
	4	4	1	0
	3	2	2	2
	3	3	2	1
	1	0	4	4
	2	3	3	1

Thanks for your help with navigation.  After writing up a reply here I did click the rating: this did take the rating, but it also erased my reply -- which I'll reconstruct.

I notice the line below the puzzle STILL says "No Solution Yet" even though the author, Josie, has confirmed the solution.  Fair enough, if the author should be the final judge whether the problem as posed has been solved.  My concern is that if the specs seem puzzling, it is sometimes interesting to see others' comments on that -- without inadvertently seeing their solutions.

For me, a Rating would combine both interest and comparative difficulty (the degree of difficulty is part of the challenge, hence interest).  Interest is of course subjective (I go for the logic and computational puzzles) , but also includes my reaction to the concept and formulation of a puzzle (I believe this type is sometimes referred to as "Hanjie" though I haven't tried them before).  I would not rate a puzzle which I was not even attempting to answer.

For the last year or so I have been participating in an online discussion of the weekly "Enigma" puzzles published in the "New Scientist".  These have a narrower scope than the puzzles here (no purely math or verbal problems), but difficulty (if genuine, and not just a product of poor wording) is part of the interest.  There are a handful of us who participate regularly, and the interest comes not so much from finding the solution, as in discussion of methods employed.  Some of us approach by developing a computer program/algorithm; others try to solve by inferences, elimination, trial-and-error etc. alone.  I see both approaches offered for the ABCD puzzle too.

Posted by ed bottemiller on 2008-03-10 09:39:20