The Great Packaging
| author |
Steve Losh <steve@stevelosh.com> |
| date |
Sat, 15 Dec 2018 16:52:29 -0500 |
| parents |
(none) |
| children |
(none) |
(defpackage :advent/2018/01 #.cl-user::*advent-use*)
(in-package :advent/2018/01)
(named-readtables:in-readtable :interpol-syntax)
(define-problem (2018 1) (data read-all)
(values
(summation data)
(progn
(setf (cdr (last data)) data) ; make data a circular list for easy looping
(iterate
(with seen = (make-hash-set :initial-contents '(0)))
(for number :in data)
(summing number :into frequency)
(if (hset-contains-p seen frequency)
(return frequency)
(hset-insert! seen frequency))))))