L-99 - Lists

L-99: Ninety-Nine Lisp Problems--or as I like to call it, I got 99 problems but a LISP ain't one--is a problem set designed to test prowess in Lisp (or Scheme, in my case), as well as algorithmic thinking. The problems are divided into subsets, each subset having a particular focus: lists, arithmetic, graphs, etc.

The first subset, comprised of problems 1 through 28, is the list-focused subset. The problems start easy; but, difficulty increases from there. Things get interesting around Problems 26 and 27, which deal with combinatoric set generation. I found Problem 27, in particular, to be challenging; and, it required a fair bit of thought to reach my current solution. The last two problems, Problems 28A and 28B, deal with sorting. I also found Problem 28B to be challenging; but, it was easier than Problem 27 to wrap my mind around. Perhaps the difference there is due simply to algorithm familiarity--which is good, when learning new things is the end game. Solutions.