Solution for the Riddler Classic problem of October 26, 2018 -- how often is it possible to start with a 6-card hand, move a clump of cards somewhere else in the hand, and end up with all suits grouped together with suits of the same color separated if possible?
Python 3 code (ran on 3.7) that solves the problem.
The output of riddler.py.
What I sent to Mr. Roeder.