Question

I am stuck on Problem Set 4, problem 4. I don't understand how to get a list of tuples, and/or how to write the recursive function.

Answer 1

Some basics on tuples:
http://www.tutorialspoint.com/python/python_tuples.htm

Answer 2

Recursive functions solve part of a problem at each level and ultimately solve the entire problem. They need to satisfy three situations: when to recurse more, when to stop recursing ( called the base case ) and what to do as the levels return ( called unwinding ).

Answer 3

Has the solution been posted for problem 4 in PS4? I have a good start on it, but I'm running into problems when trying to find the tuples for parts of the string not decrypted yet. That's the part where I need to recurse, but I haven't derived a complete approach yet.