commit ed60c55ec208cedb468617cb413076187a432b09
parent 77fbe5b8ee110dab013ddd64fbb081e9a3313138
Author: Natasha Kerensikova <natgh@instinctive.eu>
Date: Fri, 15 Dec 2023 18:49:42 +0000
Add day 14 reference and solution
Diffstat:
| A | day14.scm | | | 197 | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ |
| A | ref/day14.txt | | | 10 | ++++++++++ |
2 files changed, 207 insertions(+), 0 deletions(-)
diff --git a/day14.scm b/day14.scm
@@ -0,0 +1,197 @@
+; 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
+ srfi-69)
+
+;;;;;;;;;;;;;;;;;
+;; Input parsing
+
+(define symbol
+ (in #\. #\# #\O))
+
+(define line
+ (sequence* ((symbols (zero-or-more symbol))
+ (_ (is #\newline)))
+ (result symbols)))
+
+(define all-data
+ (zero-or-more line))
+
+(define data (parse all-data (read-string)))
+
+(define (draw-area prefix m)
+ (unless (null? m)
+ (write-line (conc prefix (list->string (car m))))
+ (draw-area prefix (cdr m))))
+
+;(write-line "Input:")
+;(draw-area " " data)
+
+;;;;;;;;;;;;;;;;;
+;; First Puzzle
+
+(define width (length (car data)))
+(define height (length data))
+(define (index-xy x y) (+ x (* width y)))
+(define (get-xy vec x y) (vector-ref vec (index-xy x y)))
+(define (set-xy! vec x y v) (vector-set! vec (index-xy x y) v))
+
+(define data-vec
+ (let ((result (make-vector (* width height))))
+ (let loop ((x 0) (y 0) (line (car data)) (rest (cdr data)))
+ (if (null? line)
+ (if (null? rest)
+ result
+ (loop 0 (add1 y) (car rest) (cdr rest)))
+ (begin
+ (set-xy! result x y (car line))
+ (loop (add1 x) y (cdr line) rest))))))
+
+(define (iter-vec proc)
+ (let loop ((x 0) (y 0))
+ (cond ((>= y height) proc)
+ ((>= x width) (loop 0 (add1 y)))
+ (else (proc x y)
+ (loop (add1 x) y)))))
+
+(define (bump-north! vec x y)
+ (when (and (> y 0)
+ (eqv? (get-xy vec x y) #\O)
+ (eqv? (get-xy vec x (sub1 y)) #\.))
+ (set-xy! vec x y #\.)
+ (set-xy! vec x (sub1 y) #\O)
+ (bump-north! vec x (sub1 y))))
+
+(define (tilt-north! vec)
+ (iter-vec (lambda (x y) (bump-north! vec x y)))
+ vec)
+
+(define (answer-1 vec)
+ (let ((acc 0))
+ (iter-vec
+ (lambda (x y)
+ (when (eqv? (get-xy vec x y) #\O)
+ (set! acc (+ acc (- height y))))))
+ acc))
+
+(tilt-north! data-vec)
+
+(write-line (conc "First puzzle: " (answer-1 data-vec)))
+
+;;;;;;;;;;;;;;;;;
+;; Second Puzzle
+
+(define (bump! vec x y dx dy)
+ (let ((tx (+ x dx)) (ty (+ y dy)))
+ (when (and (< -1 ty height)
+ (< -1 tx width)
+ (eqv? (get-xy vec x y) #\O)
+ (eqv? (get-xy vec tx ty) #\.))
+ (set-xy! vec x y #\.)
+ (set-xy! vec tx ty #\O)
+ (bump! vec tx ty dx dy))))
+
+(define (rev-iter-vec proc)
+ (let loop ((x (- width 1)) (y (- height 1)))
+ (cond ((< y 0) proc)
+ ((< x 0) (loop (- width 1) (sub1 y)))
+ (else (proc x y)
+ (loop (sub1 x) y)))))
+
+(define (tilt! vec dx dy)
+ (if (or (> dx 0) (> dy 0))
+ (rev-iter-vec (lambda (x y) (bump! vec x y dx dy)))
+ (iter-vec (lambda (x y) (bump! vec x y dx dy)))))
+
+(define (finish-cycle! vec)
+ (tilt! vec -1 0)
+ (tilt! vec 0 1)
+ (tilt! vec 1 0))
+
+(define (cycle! vec)
+ (tilt! vec 0 -1)
+ (finish-cycle! vec))
+
+(finish-cycle! data-vec)
+
+(define (draw-area-vec vec)
+ (let outer-loop ((index 0))
+ (unless (>= index (* width height))
+ (let inner-loop ((x (- width 1)) (acc '()))
+ (if (< x 0)
+ (write-line (list->string acc))
+ (inner-loop (sub1 x) (cons (vector-ref vec (+ index x)) acc))))
+ (outer-loop (+ index width)))))
+
+;(draw-area-vec data-vec)
+;(write-line "---")
+;(tilt! data-vec -1 0)
+;(draw-area-vec data-vec)
+;(write-line "---")
+;(tilt! data-vec 0 1)
+;(draw-area-vec data-vec)
+
+(define (save!-and-equal? source target)
+ (let loop ((index (- (* width height) 1)) (result #t))
+ (if (< index 0)
+ result
+ (let* ((val (vector-ref source index))
+ (next-result (and result (eqv? (vector-ref target index) val))))
+ (vector-set! target index val)
+ (loop (sub1 index) next-result)))))
+
+(define (vector-sig vec)
+ (let loop ((index 0) (acc 0))
+ (if (>= index (vector-length vec))
+ acc
+ (loop (add1 index)
+ (+ (case (vector-ref vec index)
+ ((#\.) 0)
+ ((#\#) 1)
+ ((#\O) 2)
+ (else (assert #f)))
+ (* 3 acc))))))
+
+(define memo (make-hash-table))
+(define memo-period 0)
+(define memo-length 0)
+
+(define start-sig (vector-sig data-vec))
+
+(let fill-memo ((n 1) (sig start-sig))
+ (if (hash-table-exists? memo sig)
+ (begin
+ (set! memo-length n)
+ (set! memo-period (- n (cadr (hash-table-ref memo sig))))
+ (write-line (conc "Memo table filled in " n " cycles, "
+ " period " memo-period)))
+ (begin
+ (cycle! data-vec)
+ (let ((new-sig (vector-sig data-vec)))
+ (hash-table-set! memo sig (list new-sig n (answer-1 data-vec)))
+ (fill-memo (add1 n) new-sig)))))
+
+(define (answer-2 sig n)
+ (cond ((> n (+ memo-period memo-length))
+ (answer-2 sig
+ (+ memo-length
+ (remainder (- n memo-length) memo-period))))
+ ((= n 1) (caddr (hash-table-ref memo sig)))
+ (else (answer-2 (car (hash-table-ref memo sig)) (sub1 n)))))
+
+(write-line (conc "Second puzzle: " (answer-2 start-sig (- 1000000000 1))))
diff --git a/ref/day14.txt b/ref/day14.txt
@@ -0,0 +1,10 @@
+O....#....
+O.OO#....#
+.....##...
+OO.#O....O
+.O.....O#.
+O.#..O.#.#
+..O..#O..O
+.......O..
+#....###..
+#OO..#....
