2 files changed, 500 insertions, 0 deletions
diff --git a/users/sterni/exercises/aoc/2021/default.nix b/users/sterni/exercises/aoc/2021/default.nix
new file mode 100644
index 000000000000..d3ed563ec6f8
--- /dev/null
+++ b/users/sterni/exercises/aoc/2021/default.nix
@@ -0,0 +1,10 @@
+{ depot ? import ../../../../.. { }
+, pkgs ? depot.third_party.nixpkgs
+, ...
+}:
+
+pkgs.mkShell {
+  nativeBuildInputs = [
+    pkgs.cbqn
+  ];
+}
diff --git a/users/sterni/exercises/aoc/2021/solutions.bqn b/users/sterni/exercises/aoc/2021/solutions.bqn
new file mode 100755
index 000000000000..4cedb567f9aa
--- /dev/null
+++ b/users/sterni/exercises/aoc/2021/solutions.bqn
@@ -0,0 +1,490 @@
+#!/usr/bin/env BQN
+
+#
+# Utilities
+#
+
+IsAsciiNum ← ('0'⊸≤∧≤⟜'9')
+
+ReadInt ← {(𝕨⊸×+⊣)´∘⌽-⟜'0'𝕩} # stolen from leah2
+ReadDec ← 10⊸ReadInt
+
+ReadInput ← {•file.Lines ∾ •path‿"/input/day"‿(•Fmt 𝕩)}
+
+SplitOn ← ((⊢ (-1˙)⍟⊣¨ +`∘(1⊸»<⊢))∘(≡¨)⊔⊢)
+
+_fix ← {𝕩 𝕊∘⊢⍟≢ 𝔽 𝕩}
+
+#
+# 2021-12-01
+#
+
+# part 1
+
+day1ExampleInput ← 199‿200‿208‿210‿200‿207‿240‿269‿260‿263
+day1Input ← ReadDec¨ReadInput 1
+
+# NB: Because distance from the ground is never smaller than zero, it's
+# no problem that nudge inserts a zero at the end of the right list
+PositiveDeltaCount ← +´∘(⊢<«)+˝˘∘↕
+
+! 7 = 1 PositiveDeltaCount day1ExampleInput
+
+•Out "Day 1.1: "∾•Fmt 1 PositiveDeltaCount day1Input
+
+# part 2
+
+! 5 = 3 PositiveDeltaCount day1ExampleInput
+
+•Out "Day 1.2: "∾•Fmt 3 PositiveDeltaCount day1Input
+
+#
+# 2021-12-02
+#
+
+# part 1
+
+day2ExampleInput ← ⟨
+  "forward 5",
+  "down 5",
+  "forward 8",
+  "up 3",
+  "down 8",
+  "forward 2",
+⟩
+
+day2Input ← ReadInput 2
+
+ParseSubmarineCommand ← (((↕2)⊸((((-1)⊸⋆)∘(2⊸|))×(=⟜(⌊∘(÷⟜2))))∘("duf"⊸⊐)∘⊑)×ReadDec∘(IsAsciiNum/⊢))
+
+SubmarineDestProduct ← {×´+´ParseSubmarineCommand¨𝕩}
+
+! 150 = SubmarineDestProduct day2ExampleInput
+
+•Out "Day 2.1: "∾•Fmt SubmarineDestProduct day2Input
+
+# part 2
+
+SubmarineAimedDestProduct ← {
+  ×´+´((×´)∘(1⊸↓)≍(1⊸⊑))¨ (<0‿0‿0) (⊢∾((⊑∘⌽⊣)+(⊑⊢)))` ParseSubmarineCommand¨𝕩
+}
+
+! 900 = SubmarineAimedDestProduct day2ExampleInput
+
+•Out "Day 2.2: "∾•Fmt SubmarineAimedDestProduct day2Input
+
+#
+# 2021-12-03
+#
+
+BinTable ← '0'-˜>
+
+day3ExampleInput ← BinTable ⟨
+  "00100",
+  "11110",
+  "10110",
+  "10111",
+  "10101",
+  "01111",
+  "00111",
+  "11100",
+  "10000",
+  "11001",
+  "00010",
+  "01010",
+⟩
+
+day3Input ← BinTable ReadInput 3
+
+DeBinList ← ((2⊸×)+⊣)´⌽
+_tableAggr ← {((÷⟜2)∘(/⟜⥊)´∘⌽∘≢𝔽(+˝))𝕩}
+GammaRate ← < _tableAggr
+
+! 22 = DeBinList GammaRate day3ExampleInput
+! 9  = DeBinList ¬GammaRate day3ExampleInput
+
+•Out "Day 3.1: "∾•Fmt (¬×○DeBinList⊢) GammaRate day3Input
+
+_lifeSupportRating ← {
+  # Need to rename the arguments, otherwise the ternary expr becomes a function
+  bitPos ← 𝕨
+  Cmp ← 𝔽
+
+  crit ← Cmp _tableAggr 𝕩
+  matchPos ← bitPos ⊑˘ crit ((⥊˜⟜≢)=⊢) 𝕩
+  match ← matchPos/𝕩
+  {1=≠match?⊏match;(bitPos+1) Cmp _lifeSupportRating match}
+}
+
+OxygenGeneratorRating ← DeBinList 0 ≤_lifeSupportRating ⊢
+CO2ScrubberRating ← DebinList 0 >_lifeSupportRating ⊢
+
+! 23 = OxygenGeneratorRating day3ExampleInput
+! 10 = CO2ScrubberRating day3ExampleInput
+
+•Out "Day 3.2: "∾•Fmt (OxygenGeneratorRating×CO2ScrubberRating) day3Input
+
+#
+# 2021-12-04
+#
+
+day4Numbers ← ReadDec¨ ',' SplitOn ⊑ReadInput 4
+day4Boards ← ReadDec¨>˘(' '⊸SplitOn¨)> (<⟨⟩) SplitOn 2↓ReadInput 4
+
+BoardWins ← {C ← ∨´∘(∧´˘) ⋄ (C∨C∘⍉)𝕩}
+
+_CallNumber ← {(𝕗∊⥊𝕩) (∨⍟(¬∘BoardWins∘⊢))˘ 𝕨}
+
+BoardWinScores ← {
+  𝕩 (0⊸</×) (⊢-») (+´)∘(BoardWins˘/(+´⥊)˘∘(𝕨⊸×⟜¬))¨ (<0⥊˜≢𝕨) (𝕨 _CallNumber)`𝕩
+}
+
+day4WinScores ← day4Boards BoardWinScores day4Numbers
+
+•Out "Day 4.1: "∾•Fmt ⊑day4WinScores
+•Out "Day 4.2: "∾•Fmt ⊑⌽day4WinScores
+
+#
+# 2021-12-06
+#
+
+day6ExampleInput ← ⟨3,4,3,1,2⟩
+day6Input ← ReadDec¨ ',' SplitOn ⊑ReadInput 6
+
+LanternfishPopulation ← {+´ (1⊸⌽+(⊑×((6⊸=)∘↕∘≠)))⍟𝕨 9↑≠¨⊔ 𝕩}
+
+! 26 = 18 LanternfishPopulation day6ExampleInput
+! 5934 = 80 LanternfishPopulation day6ExampleInput
+
+•Out "Day 6.1: "∾•Fmt 80 LanternfishPopulation day6Input
+•Out "Day 6.2: "∾•Fmt 256 LanternfishPopulation day6Input
+
+#
+# 2021-12-07
+#
+
+# part 1
+
+day7ExampleInput ← ⟨16,1,2,0,4,2,7,1,2,14⟩
+day7Input ← ReadDec¨ ','  SplitOn ⊑ReadInput 7
+
+PossiblePositions ← (⌊´+⟜(↕1⊸+)⌈´)
+FuelConsumption ← +˝∘|∘(-⌜)
+_lowestFuelPossible ← {⌊´∘(𝔽⟜PossiblePositions)˜ 𝕩}
+
+! 37 = FuelConsumption _lowestFuelPossible day7ExampleInput
+
+•Out "Day 7.1: "∾•Fmt FuelConsumption _lowestFuelPossible day7Input
+
+# part 2
+
+TriNum ← 1⊸+×÷⟜2
+
+FuelConsumption2 ← +˝∘(TriNum¨)∘|∘(-⌜)
+
+! 168 = FuelConsumption2 _lowestFuelPossible day7ExampleInput
+
+•Out "Day 7.2: "∾•Fmt FuelConsumption2 _lowestFuelPossible day7Input
+
+#
+# 2021-12-09
+#
+
+# part 1
+
+ParseHeightMap ← ((≠≍(≠⊑))⥊∾)∘-⟜'0'
+
+day9ExampleInput ← ParseHeightMap ⟨
+  "2199943210",
+  "3987894921",
+  "9856789892",
+  "8767896789",
+  "9899965678"
+⟩
+day9Input ← ParseHeightMap ReadInput 9
+
+Rotate ← (⍉⌽)∘⊢⍟⊣ # counter clockwise
+LowPoints ← {∧´𝕩⊸(⊣<((-⊢) Rotate ∞⊸»˘∘Rotate˜))¨ ↕4}
+
+RiskLevelSum ← (+´⥊)∘(1⊸+×LowPoints)
+
+! 15 = RiskLevelSum day9ExampleInput
+
+•Out "Day 9.1: "∾•Fmt RiskLevelSum day9Input
+
+# part 2
+
+NumberBasins ← ((1⊸+⊒⌾⥊)×⊢)∘LowPoints
+Basins ← {𝕩⊸((<⟜9⊣)∧(«⌈»⌈«˘⌈»˘⌈⊢)∘⊢) _fix NumberBasins 𝕩}
+LargestBasinsProduct ← {×´ 3↑ ∨ 1↓ ≠¨ ⊔⥊Basins 𝕩}
+
+! 1134 = LargestBasinsProduct day9ExampleInput
+
+•Out "Day 9.2: "∾•Fmt LargestBasinsProduct day9Input
+
+#
+# 2021-12-10
+#
+
+day10ExampleInput ← ⟨
+  "[({(<(())[]>[[{[]{<()<>>",
+  "[(()[<>])]({[<{<<[]>>(",
+  "{([(<{}[<>[]}>{[]{[(<()>",
+  "(((({<>}<{<{<>}{[]{[]{}",
+  "[[<[([]))<([[{}[[()]]]",
+  "[{[{({}]{}}([{[{{{}}([]",
+  "{<[[]]>}<{[{[{[]{()[[[]",
+  "[<(<(<(<{}))><([]([]()",
+  "<{([([[(<>()){}]>(<<{{",
+  "<{([{{}}[<[[[<>{}]]]>[]]",
+⟩
+day10Input ← ReadInput 10
+
+# part 1
+
+opp ← "([{<"
+clp ← ")]}>"
+SwapParen ← (opp∾⌽clp)⊸((⊑⊐)⊑(⌽⊣))
+
+ParenStacks ← ((<⟨⟩)⊸(((⊑∊)⟜clp⊢)◶(∾˜⟜SwapParen)‿(1⊸↓⊣)`))
+LegalParens ← ((1⊸↑)¨∘»∘ParenStacks ((∊⟜opp⊢)∨(≡⟜⋈)¨) ⊢)
+
+_ScoreFor_ ← {𝕗⊸(𝕘⊸⊐⊏⊣) 𝕩}
+
+SyntaxScore ← +´∘(0‿3‿57‿1197‿25137 _ScoreFor_ (" "∾clp))∘∾∘(1⊸↑∘(¬∘LegalParens/⊢)¨)
+
+! 26397 = SyntaxScore day10ExampleInput
+•Out "Day 10.1: "∾•Fmt SyntaxScore day10Input
+
+# part 2
+
+AutocompleteScore ← {
+  Score ← (5⊸×⊸+)˜´∘⌽∘((1+↕4) _ScoreFor_ clp)
+  # TODO(sterni): we compute ParenStacks twice here
+  ((⌊÷⟜2)∘≠⊑⊢) ∧ Score∘(⊑⌽)∘ParenStacks¨ (∧´∘LegalParens¨/⊢) 𝕩
+}
+
+! 288957 = AutocompleteScore day10ExampleInput
+•Out "Day 10.2: "∾•Fmt AutocompleteScore day10Input
+
+#
+# 2021-12-11
+#
+
+day11Input ← '0'-˜> ReadInput 11
+day11ExampleInput ← >⟨
+  ⟨5,4,8,3,1,4,3,2,2,3,⟩,
+  ⟨2,7,4,5,8,5,4,7,1,1,⟩,
+  ⟨5,2,6,4,5,5,6,1,7,3,⟩,
+  ⟨6,1,4,1,3,3,6,1,4,6,⟩,
+  ⟨6,3,5,7,3,8,5,4,7,8,⟩,
+  ⟨4,1,6,7,5,2,4,6,4,5,⟩,
+  ⟨2,1,7,6,8,4,1,7,2,1,⟩,
+  ⟨6,8,8,2,8,8,1,1,3,4,⟩,
+  ⟨4,8,4,6,8,4,8,5,5,4,⟩,
+  ⟨5,2,8,3,7,5,1,5,2,6,⟩,
+⟩
+
+# part 1
+
+OctopusFlash ← {
+  ((⥊⟜0)∘≢𝕊⊢) 𝕩;
+  flashing ← (¬𝕨)∧9<𝕩
+  energy ← ((«˘»)+(»˘«)+(»˘»)+(«˘«)+(»˘)+(«˘)+«+») flashing
+  ((𝕨∨flashing)⊸𝕊)⍟(0<+´⥊flashing) energy+𝕩
+}
+
+OctopusStep ← ((9⊸≥)×⊢)∘OctopusFlash∘(1⊸+)
+OctopusFlashCount ← {+´⥊0=>(OctopusStep⊣)`(1+𝕨)⥊<𝕩}
+
+! 1656 = 100 OctopusFlashCount day11ExampleInput
+•Out "Day 11.1: "∾•Fmt 100 OctopusFlashCount day11Input
+
+# part 2
+
+_iterCountUntil_ ← {
+  0 𝕊 𝕩;
+  𝔾◶⟨((𝕨+1)⊸𝕊)∘𝔽, 𝕨˙⟩ 𝕩
+}
+
+OctopusAllFlashing ← OctopusStep _iterCountUntil_ (∧´∘⥊∘(0⊸=))
+
+! 195 = OctopusAllFlashing day11ExampleInput
+
+•Out "Day 11.2: "∾•Fmt OctopusAllFlashing day11Input
+
+#
+# 2021-12-13
+#
+
+SplitFoldingInstructions ← ("fold along"⊸(⊣≡≠⊸↑)¨⊔⊢)∘(0⊸(≠⟜≠¨/⊢))
+day13ExampleInput ← SplitFoldingInstructions ⟨
+  "6,10",
+  "0,14",
+  "9,10",
+  "0,3",
+  "10,4",
+  "4,11",
+  "6,0",
+  "6,12",
+  "4,1",
+  "0,13",
+  "10,12",
+  "3,4",
+  "3,0",
+  "8,4",
+  "1,10",
+  "2,14",
+  "8,10",
+  "9,0",
+  "",
+  "fold along y=7",
+  "fold along x=5",
+⟩
+day13Input ← SplitFoldingInstructions ReadInput 13
+
+ParseDots ← ReadDec¨∘(','⊸SplitOn)¨
+ParseFolds ← (⊑∘'y'⊸∊≍ReadDec∘(IsAsciiNum/⊢))¨
+day13ExampleDots ← ParseDots ⊑ day13ExampleInput
+
+# part 1
+
+# 𝕨=0 => x, 𝕨=1 => y
+# 𝕩 is coordinate to fold around
+# 𝕗 is input dot list (see ParseDots)
+_Fold ← {⍷∘((𝕩⊸(((2⊸×⊣)-⊢)⌊⊢)∘⊑≍1⊸⊑)¨⌾(⌽¨⍟𝕨)) 𝕗}
+
+! 17 = ≠ 1 day13ExampleDots _Fold 7
+
+day13Dots ← ParseDots ⊑ day13Input
+day13Folds ← ParseFolds 1 ⊑ day13Input
+
+•Out "Day 13.1: "∾•Fmt ≠ (day13Dots _Fold)´ ⊑day13Folds
+
+# part 2
+
+PerformAllFolds ← {𝕩 {(𝕨 _Fold)´𝕩}˜´ ⌽𝕨}
+DotMatrix ← {
+  ⟨width, height⟩ ← 1+⌈˝∘‿2⥊∾𝕩
+  {𝕩? '█';' '}¨ height‿width⥊≠¨⊔((⊣+(width⊸×)∘⊢)´)¨ 𝕩
+}
+
+•Out "Day 13.2:"
+•Out •Fmt DotMatrix day13Folds PerformAllFolds day13Dots
+
+#
+# 2021-12-14
+#
+
+day14Polymer ← ⊑ReadInput 14
+day14Mapping ← 2↓ReadInput 14
+
+lp ← (2⊸↑)¨ day14Mapping
+le ← ⍷∾lp
+
+# returns array as long as 𝕨 detailing how many times the element
+# at any given index occurs in 𝕩.
+Counts ← ((≠⊣)↑(/⁼)∘⊐)
+
+deltaPairs ← {
+  addedPairs ← ((-1)⊸⊑¨day14Mapping) (⌽⌾(0⊸⊑))∘(∾¨)¨ lp
+  removedPairs ← ⋈¨ (2⊸↑)¨ lp
+  addedPairs (-○(lp⊸Counts))¨ removedPairs
+}
+
+pairCount ← lp Counts ⥊∘(⋈˘) 2↕day14Polymer
+
+PairInsert ← {𝕩 +´ 𝕩×¨deltaPairs}
+
+pairElementCount ← (le⊸Counts)¨lp
+
+ElementRarityDiff ← {
+ ((-1)⊸⊑-⊑)∧ ⌈2÷˜ +´ pairElementCount×PairInsert⍟𝕩 pairCount
+}
+
+•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
+
+#
+# 2021-12-20
+#
+
+ParsePic ← (⋈⟜0)∘('#'⊸=)∘>
+
+day20ExampleAlgo ← '#'="..#.#..#####.#.#.#.###.##.....###.##.#..###.####..#####..#....#..#..##..###..######.###...####..#..#####..##..#.#####...##.#.#..#.##..#.#......#.###.######.###.####...#.##.##..#..#..#####.....#.#....###..#.##......#.....#..#..#..##..#...##.######.####.####.#.#...#.......#..#.#.#...####.##.#......#..#...##.#.##..#...##.#.##..###.#......#.#.......#.#.#.####.###.##...#.....####.#..#..#.##.#....##..#.####....##...##..#...#......#.#.......#.......##..####..#...#.#.#...##..#.#..###..#####........#..####......#..#"
+day20ExamplePic ← ParsePic ⟨"#..#.", "#....", "##..#", "..#..", "..###"⟩
+day20Input ← ReadInput 20
+day20Algo ← '#'=⊑day20Input
+day20Pic ← ParsePic 2↓day20Input
+
+GrowAxis ← {(⊢ (-1)⊸⌽∘∾ (⥊⟜𝕨)∘(2˙⌾⊑)∘≢) 𝕩}
+Grow ← {𝕨 GrowAxis 𝕨 GrowAxis˘ 𝕩}
+
+Enhance ← {
+  inf ← 1⊑𝕩
+  npic ← ((⊑⟜𝕨)∘DebinList∘⥊)˘˘ 3‿3↕ (inf⊸Grow)⍟2 ⊑𝕩
+  ninf ← 𝕨⊑˜511×inf
+  npic⋈ninf
+}
+_EnhancedPixelCount ← {+´⥊⊑ (𝕨⊸Enhance)⍟𝕗 𝕩}
+
+! 35 = day20ExampleAlgo 2 _EnhancedPixelCount day20ExamplePic
+! 3351 = day20ExampleAlgo 50 _EnhancedPixelCount day20ExamplePic
+
+•Out "Day 20.1: "∾•Fmt day20Algo 2 _EnhancedPixelCount day20Pic
+•Out "Day 20.2: "∾•Fmt day20algo 50 _EnhancedPixelCount day20Pic
+
+#
+# 2021-12-25
+#
+
+day25Input ← ".>v" ⊐ > ReadInput 25
+day25ExampleInput ← ".>v"⊐∘‿10⥊"v...>>.vv>.vv>>.vv..>>.>v>...v>>v>>.>.v.v>v.vv.v..>.>>..v....vv..>.>v.v.v..>>v.v....v..v.>"
+
+Xor ← (¬⊸∧∨∧⟜¬)
+MoveHerd ← {(𝕩∧𝕩≠𝕨)+𝕨× (𝕨=𝕩) (Xor⟜(1⊸⌽)∨⊢) (0=𝕩)∧(-1)⌽𝕨=𝕩}
+
+_fixCount ← {
+  1 𝕊 𝕩;
+  𝕩 ≡◶⟨(𝕨+1)⊸𝕊, 𝕨˙⟩ 𝔽 𝕩
+}
+
+MoveAllHerds ← (2⊸MoveHerd)∘(1⊸MoveHerd˘)
+
+! 58 = MoveAllHerds _fixCount day25ExampleInput
+•Out "Day 25.1: "∾•Fmt MoveAllHerds _fixCount day25Input