hg.stevelosh.com > advent

src/2018/days/day-01.lisp @ cd781337a694 

Restructure file layout, add 2017 days 14 & 15
author Steve Losh <steve@stevelosh.com>
date Thu, 05 Dec 2019 20:45:46 -0500
parents src/2018/day-01.lisp@5b5c61ad8d2b
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))))))