1 files changed, 35 insertions, 0 deletions
diff --git a/users/sterni/exercises/aoc/2021/solutions.bqn b/users/sterni/exercises/aoc/2021/solutions.bqn
index f240e7dc2d..83949daa11 100755
--- a/users/sterni/exercises/aoc/2021/solutions.bqn
+++ b/users/sterni/exercises/aoc/2021/solutions.bqn
@@ -278,3 +278,38 @@ ElementRarityDiff ← {
 
 •Out "Day 14.1: "∾•Fmt ElementRarityDiff 10
 •Out "Day 14.2: "∾•Fmt ElementRarityDiff 40
+
+#
+# 2021-12-15
+#
+
+day15ExampleInput ← >⟨
+  1‿1‿6‿3‿7‿5‿1‿7‿4‿2
+  1‿3‿8‿1‿3‿7‿3‿6‿7‿2
+  2‿1‿3‿6‿5‿1‿1‿3‿2‿8
+  3‿6‿9‿4‿9‿3‿1‿5‿6‿9
+  7‿4‿6‿3‿4‿1‿7‿1‿1‿1
+  1‿3‿1‿9‿1‿2‿8‿1‿3‿7
+  1‿3‿5‿9‿9‿1‿2‿4‿2‿1
+  3‿1‿2‿5‿4‿2‿1‿6‿3‿9
+  1‿2‿9‿3‿1‿3‿8‿5‿2‿1
+  2‿3‿1‿1‿9‿4‿4‿5‿8‿1
+⟩
+day15Input ← '0'-˜ ((≠⋈≠∘⊑)⥊∾)ReadInput 15
+
+LowestRiskLevel ← {
+  start ← 0˙⌾⊑ (⥊⟜∞) ≢𝕩
+  ir ← (1⊑≢𝕩)⥊∞
+  Step ← {𝕩 ⌊ 𝕨 + (ir⊸«⌊ir⊸»⌊∞⊸«˘⌊∞⊸»˘) 𝕩}
+  ⊑⌽⥊ 𝕩⊸Step _fix start
+}
+
+! 40 = LowestRiskLevel day15ExampleInput
+
+•Out "Day 15.1: "∾•Fmt LowestRiskLevel day15Input
+
+FiveByFiveMap ← {(9⊸|)⌾(-⟜1) ∾(<𝕩)+ +⌜˜↕5}
+
+! 315 = LowestRiskLevel FiveByFiveMap day15ExampleInput
+
+•Out "Day 15.2: "∾•Fmt LowestRiskLevel FiveByFiveMap day15Input