From de3954129bfa3a746a313181cae71e1f384dda59 Mon Sep 17 00:00:00 2001
From: lamp
Date: Wed, 6 Dec 2023 20:14:46 +0000
Subject: add day 6 solutions

---
 6-2.scm | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)
 create mode 100755 6-2.scm

(limited to '6-2.scm')

diff --git a/6-2.scm b/6-2.scm
new file mode 100755
index 0000000..71279a7
--- /dev/null
+++ b/6-2.scm
@@ -0,0 +1,30 @@
+#!/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)))))
-- 
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