src/2018/days/day-01.lisp @ 0a241f64eebb
2016/01
author |
Steve Losh <steve@stevelosh.com> |
date |
Fri, 06 Dec 2019 20:57:40 -0500 |
parents |
cd781337a694 |
children |
182bdd87fd9e |
(defpackage :advent/2018/01 #.cl-user::*advent-use*)
(in-package :advent/2018/01)
(define-problem (2018 1) (data read-all) (522 73364)
(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))))))