This probably shouldn't be the first example, but it's a nice one:
===
My requirement was
I want a list of all ordered permutations of a given length of a set of tokens. Each token is a single character, and for convenience, they are passed as a string in ascending ASCII order.
For example
permute("abc",2)
should return ["aa","ab","ac","ba","bb","bc","ca","cb","cc"]
and permute("13579",3) should return a list of 125 elements
["111","113", ... ,"997","999"]
===
Ask the experienced coder to code this up in the language of his or her choice. Then show them this (contributed by castironpi):
{ { {
- def p(a,b):
if not b: return [] return [i+j for i in a for j in p(a,b-1)]
} } }