From: Ben Harris <bjh21@bjh21.me.uk>
Date: Thu, 30 May 2024 19:45:16 +0000 (+0100)
Subject: 20a done
X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~bjharris/git?a=commitdiff_plain;h=85499f93fa2f62c088f8315b0ade69889df96d70;p=aoc-2022.git

20a done

Thanks to cardboard Verity for providing the answer, which is that it
doesn't matter where the start of the list is: everything treats it as
circular.
---

diff --git a/20/20a.bqn b/20/20a.bqn
index a7686ae..26218d9 100644
--- a/20/20a.bqn
+++ b/20/20a.bqn
@@ -1,14 +1,8 @@
 Prep←•ParseFloat¨
 
 Main←{ 𝕊 orig:
-  Wrap←{1+(𝕨-1)|𝕩-1}
-  Jump←{
-    from ← ⊑𝕩⊐𝕨
-    to ← (≠𝕩) Wrap 𝕨+from
-    len ← to-from
-    ((×len)⊸⌽) ⌾ ((1+|len)⊸↑∘((to⌊from)⊸↓)) 𝕩
-  }
-  cur ← orig Jump´ ⌽orig
+  Twiddle←{ (1⊸⌽)⌾((1+(¯1+≠𝕩)|𝕨)⊸↑) (⊑𝕩⊐𝕨)⌽𝕩 }
+  cur ← orig Twiddle´ ⌽orig
   +´((≠cur)|(cur⊐0)+⟨1000,2000,3000⟩)⊏cur
 }