src/2021/days/day-02.lisp @ fe0e8fa1b37d
2021/09
author |
Steve Losh <steve@stevelosh.com> |
date |
Wed, 08 Dec 2021 21:47:41 -0800 |
parents |
bd509ececdf0 |
children |
(none) |
(advent:defpackage* :advent/2021/02)
(in-package :advent/2021/02)
(defun parse (stream)
(iterate (for line :in-stream stream :using #'read-line)
(ppcre:register-groups-bind ((#'ensure-keyword command) (#'parse-integer n))
("(\\w+) (\\d+)" line)
(collect (cons command n)))))
(defun horiz (pos) (realpart pos))
(defun depth (pos) (imagpart pos))
(defun part1 (course)
(iterate (for (cmd . n) :in course)
(summing (ecase cmd
(:forward (complex n 0))
(:down (complex 0 n))
(:up (complex 0 (- n)))))))
(defun part2 (course)
(iterate (with pos = 0)
(with aim = 0)
(for (cmd . n) :in course)
(ecase cmd
(:forward (incf pos (complex n (* n aim))))
(:down (incf aim n))
(:up (decf aim n)))
(returning pos)))
(define-problem (2021 2) (data) (1660158 1604592846)
(let* ((course (parse data))
(p1 (part1 course))
(p2 (part2 course)))
(values (* (horiz p1) (depth p1))
(* (horiz p2) (depth p2)))))
#; Scratch --------------------------------------------------------------------