I'd have to question picking any single programming problem like the one mentioned is a great proxy for IQ. Could it be that there's a class of problems or conc

I'd have to question picking any single programming problem like the one mentioned is a great proxy for IQ. Could it be that there's a class of problems or conceptual framework (in this case, maybe combinations/permutations or tree traversal), where a person might have solved a dozen problems like this in the past, and this is just another slightly different one?