In the course of some research on the Internet, I came across a San Francisco-based firm called Loomia, which provides companies with software to do those "If you liked this, then you'll also like..." blurbs on their websites. Curious about the company, I poked around their website to learn more, which led me to their "Tech Challenge Questions" for prospective employees.

Some of the questions were quite clever, though I really liked one in particular, which I will post here, with some modifications in the phrasing.

Challenge: Given the set { a, b, c, ... , z }, the set of lowercase letters of the standard English alphabet, we then define the operation $. Suppose we only know that

a $ b = ab = a
bc = c
cd = g
ef = u
ee = q
wy = i
wn = a
pq = g
rm = w
zc = y

and that the operation $ is associative with the identity element b. What, then, are the values of faulkner, oconnor and welty ?

It's not a particularly difficult to reverse engineer the operator, but I thought it was amusing enough to merit my repeating it.