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Add day 1

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cælōrum spectātrīx 2025-12-01 19:52:45 +01:00
parent 08606832f8
commit ce1af441c4
1 changed files with 60 additions and 0 deletions
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1/main.scm Normal file
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(import (scheme base)
(scheme file)
(scheme process-context)
(scheme write))
(include "../common.scm")
(define (direction->arithmetic direction)
(cond
((char=? direction #\L) -)
((char=? direction #\R) +)))
(define (part1 file)
(with-input-from-file file
(lambda ()
(let loop ((dial 50)
(line (read-line))
(zeros 0))
(if (eof-object? line)
(number->string zeros)
(let* ((direction (string-ref line 0))
(distance (string->number (substring line 1 (string-length line))))
(new-dial (modulo ((direction->arithmetic direction) dial distance) 100)))
(loop new-dial (read-line) (if (zero? new-dial) (+ 1 zeros) zeros))))))))
(define (pseudo-modulo/count-wraps a b)
(let loop ((n a)
(wraps 0))
(cond
((zero? n)
(values n (+ 1 wraps)))
((negative? n)
(loop (+ n b) (+ 1 wraps)))
((= n b)
(values 0 (+ 1 wraps)))
((> n b)
(loop (- n b) (+ 1 wraps)))
(else
(values n wraps)))))
;; Could be improved...
(define (part2 file)
(with-input-from-file file
(lambda ()
(let loop ((dial 50)
(zeros 0)
(line (read-line)))
(if (eof-object? line)
(number->string zeros)
(let* ((direction (string-ref line 0))
(distance (string->number (substring line 1 (string-length line))))
(dial+-distance ((direction->arithmetic direction) dial distance)))
(let-values (((new-dial add-zeros) (pseudo-modulo/count-wraps dial+-distance 100)))
(loop new-dial
(+ zeros add-zeros (if (and (zero? dial) (negative? dial+-distance)) -1 0))
(read-line)))))))))
(for-each print (map part1 (command-line-arguments)))
(for-each print (map part2 (command-line-arguments)))