Given a list of strings, e.g. 'cat', 'dog', 'bobo', 'dada', 'abad', 'cbcf', combine set of words that have have the same pattern. So, in this case you'd have: ['cat', 'dog'], ['bobo', 'dada'], and ['abad', 'cbcf']. Not much information was given beyond this and I had to probe the interviewer for more details