Dear Joshua: I don't understand the description of your rule. Do you mean _any_ k cells, whether or not they're in rows, columns or blocks? Furthermore, what do you mean by "at most k" ? At 08:51 AM 6/30/2006, Joshua Zucker wrote:

I'm not clear from your description of level 1 whether you look at every set of k cells -- if a set of k cells out of 9 includes at most k different digits, then those k digits can't appear anywhere else in the set of 9. (I was very pleased when I realized that this rule with k = 1 and k = 8 covered the two usual simplest rules, "if a cell can contain only one digit..." and "if a digit can appear in only one cell...")

--Joshua Zucker