Submissions for the Foobar with Google code challenge.
I was invited to take part of the Foobar.withgoogle Code Challenge after googling "python list comprehension"
While I feel that I was an outlier in their model, and given the current employment climate in tech and Googles notoriously difficult technical interviews, I've still chosen to do the challenges as time permits as they are pretty fun and I haven't written in Java in a long time.
Note that solution3a did not pass all of the hidden tests, as I believe it violates space requirements on the stack (my solution is recursive and the stackoverflow iterative approach passed all of the tests)