commit 5ade9b08107717f9ddd2222eadf5ff5393113d1b
from: Lukas Henkel <lh@entf.net>
date: Wed Dec 06 19:35:22 2023 UTC

Range is symmetrical

commit - d2f25f66d712a2d3cfdfa79a23a4df06dc2d8922
commit + 5ade9b08107717f9ddd2222eadf5ff5393113d1b
blob - e82dbf124ff526f0b4a7da01956dff6ff19c852d
blob + 24dd6c13affbeb00505d257902c191959f0f696b
--- src/day-6.lisp
+++ src/day-6.lisp
@@ -14,11 +14,8 @@
 (defun possible-ways-to-beat (time distance)
   (let ((start (loop for speed from 1 below time
                      when (beats-distance-p speed time distance)
-                       do (return speed)))
-        (end (loop for speed from (1- time) downto 1
-                   when (beats-distance-p speed time distance)
-                     do (return speed))))
-    (- end start -1)))
+                       do (return speed))))
+    (- time (* start 2) -1)))
 
 (defun join-numbers (numbers)
   (parse-integer (apply 'concatenate 'string