feat: learn from dzaima's solution of day 16.

src/aoc24.org

@@ -338,6 +338,26 @@ powers of the adjacency matrix. This method is unfortunately slower than simple
 #+RESULTS:
 : "Computed 1446158 and 1446175 in 0.0177348094s"
 
+** XVI
+
+I dislike graph algorithms for their messy, imperative solutions with impurities and fancy data structures.
+This problem is usually solved with Dijkstra, but after days of "Fortranized" DFS and BFS, I turned to an
+expert array programmer's [[https://github.com/dzaima/aoc][solution]] and reworked mine:
+
+#+begin_src bqn :tangle ./bqn/aoc24.bqn :exports both
+  XVI ← {
+    r‿s‿e ← ⟨'#'⊸≠, 'S'⊸=, 'E'⊸=⟩{𝕎𝕩}¨<inp ← >•FLines Input𝕩
+    _fp ← {𝔽∘⊢⍟≢⟜𝔽_𝕣∘⊢⍟≢⟜𝔽𝕩} ⋄ _m ← {𝕩{𝕏𝕨}¨𝔽⟨»,»˘,«,«˘⟩} ⋄ inf ← -2⋆31
+    dij ← ⌊´∘{⟨⊢_m, 1⊸⌽⌊1⊸⌽⁼, ⊢⟩{r<⊸×𝕎𝕩}¨⟨𝕩+1, 𝕩+1e3, 𝕩⟩}_fp 0‿inf‿0‿0×<s
+    mn‿mr‿mrc ← r⊸∧¨¨ {⟨¯1+2⊸⌽_m𝕩, 1⌽𝕩-1e3, 1⌽⁼𝕩-1e3⟩=<𝕩}dij
+    eins ⇐ inf -˜ opt ← (⌊´dij) ⊑˜⊑/○⥊⟜(↕≢)e
+    zwei ⇐ +´⥊∨´ {∨´⟨mn∧2⊸⌽𝕩, mr∧1⌽𝕩, mrc∧1⌽⁼𝕩, 𝕩⟩}_fp e<⊸∧dij=opt
+  }
+  XVI _is 16
+#+end_src
+
+#+RESULTS:
+: "Computed 99448 and 1 in 0.049628195s"
 
 #+BEGIN_EXPORT html
   <div style="text-align: center; font-size: 2em; padding: 20px 0;">

src/bqn/aoc24.bqn

@@ -175,3 +175,13 @@ XV ← {
   w↩wd ⋄ rid DFS´m ⋄ zwei ⇐ +´⥊100‿1×⎉1>/○⥊⟜(↕≢)'['=w
 }
 XV _is 15
+
+XVI ← {
+  r‿s‿e ← ⟨'#'⊸≠, 'S'⊸=, 'E'⊸=⟩{𝕎𝕩}¨<inp ← >•FLines Input𝕩
+  _fp ← {𝔽∘⊢⍟≢⟜𝔽_𝕣∘⊢⍟≢⟜𝔽𝕩} ⋄ _m ← {𝕩{𝕏𝕨}¨𝔽⟨»,»˘,«,«˘⟩} ⋄ inf ← -2⋆31
+  dij ← ⌊´∘{⟨⊢_m, 1⊸⌽⌊1⊸⌽⁼, ⊢⟩{r<⊸×𝕎𝕩}¨⟨𝕩+1, 𝕩+1e3, 𝕩⟩}_fp 0‿inf‿0‿0×<s
+  mn‿mr‿mrc ← r⊸∧¨¨ {⟨¯1+2⊸⌽_m𝕩, 1⌽𝕩-1e3, 1⌽⁼𝕩-1e3⟩=<𝕩}dij
+  eins ⇐ inf -˜ opt ← (⌊´dij) ⊑˜⊑/○⥊⟜(↕≢)e
+  zwei ⇐ +´⥊∨´ {∨´⟨mn∧2⊸⌽𝕩, mr∧1⌽𝕩, mrc∧1⌽⁼𝕩, 𝕩⟩}_fp e<⊸∧dij=opt
+}
+XVI _is 16