commit 8b7410f8cfe8470d79be5ad9588cc933757e34f4
parent 66c663e2bff18197bb561e4264851f536fbf8b5e
Author: Natasha Kerensikova <natgh@instinctive.eu>
Date: Wed, 6 Dec 2023 18:13:47 +0000
Add day 6 reference and solution
Diffstat:
2 files changed, 77 insertions(+), 0 deletions(-)
diff --git a/2023/day06.scm b/2023/day06.scm
@@ -0,0 +1,75 @@
+; Copyright (c) 2023, Natacha Porté
+;
+; Permission to use, copy, modify, and distribute this software for any
+; purpose with or without fee is hereby granted, provided that the above
+; copyright notice and this permission notice appear in all copies.
+;
+; THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+; WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+; MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+; ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+; WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+; ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+; OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+(import (chicken io) (chicken string)
+ comparse
+ srfi-1
+ srfi-14)
+
+;;;;;;;;;;;;;;;;;
+;; Input parsing
+
+(define (as-number parser)
+ (bind (as-string parser)
+ (lambda (s)
+ (result (string->number s)))))
+
+(define spaces
+ (one-or-more (is #\space)))
+
+(define digit
+ (in char-set:digit))
+
+(define digits
+ (as-number (one-or-more digit)))
+
+(define (prefixed-list prefix)
+ (sequence* ((_ (char-seq prefix))
+ (data (zero-or-more (preceded-by spaces digits)))
+ (_ (is #\newline)))
+ (result data)))
+
+(define all-data
+ (sequence* ((times (prefixed-list "Time:"))
+ (dists (prefixed-list "Distance:")))
+ (result (zip times dists))))
+
+(define data (parse all-data (read-string)))
+(write-line (conc "Input: " data))
+
+;;;;;;;;;;;;;;;;;
+;; First Puzzle
+
+; Traveled distance: (total_time - held_time) * held_time)
+; Winning held_time when -held_time² + total_time*held_time - other_dist >0
+; So bounds are (total_time ± sqrt(total_time² - 4*other_dist))/2
+
+(define (time-breadth l)
+ (let ((total-time (car l))
+ (other-dist (cadr l)))
+ (let* ((sqrt-discr (sqrt (- (* total-time total-time) (* 4 other-dist))))
+ (lower (floor (* 0.5 (- total-time sqrt-discr))))
+ (upper (ceiling (* 0.5 (+ total-time sqrt-discr)))))
+ (- upper lower 1))))
+
+(write-line (conc "First puzzle: " (apply * (map time-breadth data))))
+
+;;;;;;;;;;;;;;;;;
+;; Second Puzzle
+
+(define concat-data
+ (list (string->number (apply conc (map car data)))
+ (string->number (apply conc (map cadr data)))))
+
+(write-line (conc "Second puzzle: " (time-breadth concat-data)))
diff --git a/2023/ref/day06.txt b/2023/ref/day06.txt
@@ -0,0 +1,2 @@
+Time: 7 15 30
+Distance: 9 40 200
