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-rwxr-xr-x6-2.scm30
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+#!/usr/bin/env -S guile -s
+!#
+(use-modules (ice-9 regex)
+ (ice-9 textual-ports)
+ (srfi srfi-1))
+
+(define (read-lines port)
+ (letrec ((loop (lambda (l ls)
+ (if (eof-object? l)
+ ls
+ (loop (get-line port) (cons l ls))))))
+ (reverse (loop (get-line port) '()))))
+
+(define (value-for-line line)
+ (string->number (string-filter char-set:digit line)))
+
+(define (travel-distance total-time hold-time)
+ (* (- total-time hold-time) hold-time))
+
+(let* ((port (open-input-file "6.txt"))
+ (lines (read-lines port))
+ (time (value-for-line (car lines)))
+ (distance (value-for-line (cadr lines)))
+ (current 0)
+ (count 0))
+ (close-port port)
+ (while (<= current distance)
+ (set! current (travel-distance time count))
+ (set! count (1+ count)))
+ (display (- (+ time 1) (* 2 (- count 1)))))