4 files changed, 769 insertions, 0 deletions
diff --git a/2020/08-Handheld_Halting/example b/2020/08-Handheld_Halting/example
new file mode 100644
index 0000000..178df53
--- /dev/null
+++ b/2020/08-Handheld_Halting/example
@@ -0,0 +1,9 @@
+nop +0
+acc +1
+jmp +4
+acc +3
+jmp -3
+acc -99
+acc +1
+jmp -4
+acc +6
diff --git a/2020/08-Handheld_Halting/first.hs b/2020/08-Handheld_Halting/first.hs
new file mode 100644
index 0000000..3d01106
--- /dev/null
+++ b/2020/08-Handheld_Halting/first.hs
@@ -0,0 +1,57 @@
+-- requires cabal install --lib megaparsec parser-combinators
+module Main (main) where
+import Control.Monad (void, when)
+import qualified Data.Set as S
+import Data.Void (Void)
+import Text.Megaparsec
+import Text.Megaparsec.Char
+import System.Exit (die)
+
+exampleExpectedOutput = 5
+
+data Op = Nop Int | Acc Int | Jmp Int
+
+type Parser = Parsec Void String
+
+parseOp :: Parser Op
+parseOp = do
+  op <- string "nop " <|> string "acc " <|> string "jmp "
+  sign <- (char '+' *> return 1) <|> (char '-' *> return (-1))
+  num <- some digitChar
+  void $ char '\n'
+  let n = sign * (read num)
+  return $ case op of
+    "nop " -> Nop n
+    "acc " -> Acc n
+    "jmp " -> Jmp n
+
+parseOps :: Parser [Op]
+parseOps = some parseOp <* eof
+
+parseInput :: String -> IO [Op]
+parseInput filename = do
+  input <- readFile filename
+  case runParser parseOps filename input of
+    Left bundle -> die $ errorBundlePretty bundle
+    Right ops -> return ops
+
+compute :: [Op]-> Int
+compute ops = run 0 0 S.empty
+  where
+    run :: Int -> Int -> S.Set Int -> Int
+    run pointer acc visited
+      | S.member pointer visited = acc
+      | otherwise = case ops !! pointer of
+          Nop _ -> run (pointer + 1) acc visited'
+          Acc i -> run (pointer + 1) (acc + i) visited'
+          Jmp i -> run (pointer + i) acc visited'
+      where
+        visited' = S.insert pointer visited
+
+main :: IO ()
+main = do
+  example <- parseInput "example"
+  let exampleOutput = compute example
+  when  (exampleOutput /= exampleExpectedOutput)  (die $ "example failed: got " ++ show exampleOutput ++ " instead of " ++ show exampleExpectedOutput)
+  input <- parseInput "input"
+  print $ compute input
diff --git a/2020/08-Handheld_Halting/input b/2020/08-Handheld_Halting/input
new file mode 100644
index 0000000..b97230b
--- /dev/null
+++ b/2020/08-Handheld_Halting/input
@@ -0,0 +1,636 @@
+acc -13
+jmp +37
+acc -19
+jmp +1
+jmp +1
+jmp +413
+acc +10
+jmp +194
+jmp +587
+jmp +388
+acc +48
+nop +284
+acc +35
+jmp +239
+acc +0
+jmp +58
+acc +22
+acc +45
+acc +25
+acc +23
+jmp +544
+jmp +610
+nop +273
+jmp +554
+jmp +584
+acc +30
+jmp +481
+acc +29
+jmp +342
+acc +9
+acc +23
+nop +377
+jmp +483
+acc +33
+jmp +128
+nop +560
+nop +437
+jmp +485
+acc +2
+acc +30
+jmp +456
+acc +0
+acc -15
+nop +126
+acc +47
+jmp +299
+acc +36
+acc +9
+jmp -21
+acc +10
+acc +26
+acc -3
+acc +31
+jmp +337
+nop +517
+jmp +303
+acc +20
+nop -43
+acc +30
+acc +24
+jmp +348
+jmp +158
+acc +23
+acc +16
+acc +40
+jmp +1
+jmp +465
+acc +12
+jmp +276
+acc +0
+acc +32
+acc +43
+jmp +487
+acc +40
+acc +49
+nop +540
+jmp +455
+acc +24
+jmp +481
+acc +30
+nop +256
+acc +29
+acc +14
+jmp +390
+jmp +1
+acc -3
+jmp +1
+jmp +295
+acc +6
+acc +46
+acc +16
+nop +128
+jmp -38
+acc +0
+acc +16
+acc +10
+jmp +185
+acc -19
+acc +0
+acc +23
+acc -16
+jmp +180
+acc +14
+jmp +1
+acc +31
+acc -4
+jmp +439
+jmp +204
+acc +50
+acc +12
+nop +154
+jmp +474
+acc -16
+jmp +511
+acc +6
+acc +32
+jmp +504
+acc +17
+acc +21
+acc -18
+jmp +298
+acc -17
+acc +16
+acc +4
+acc +18
+jmp +18
+acc -10
+acc +26
+acc +36
+jmp +166
+nop -109
+jmp +266
+acc -9
+jmp +306
+nop +324
+acc +16
+acc +33
+acc +18
+jmp -50
+acc +25
+jmp +196
+acc +21
+jmp +308
+jmp +38
+acc +27
+jmp -48
+acc +14
+acc +46
+acc +48
+acc +15
+jmp +223
+acc +0
+acc +12
+jmp -115
+acc +19
+acc +27
+acc +30
+jmp +377
+jmp -144
+jmp +231
+acc +1
+jmp +410
+acc +41
+jmp +138
+acc -13
+acc -8
+acc -7
+acc +25
+jmp +366
+acc +8
+jmp +182
+acc +2
+nop +104
+acc +24
+acc +21
+jmp -43
+acc -8
+acc +37
+acc +23
+jmp +292
+jmp +365
+acc +33
+nop -144
+acc -10
+jmp +387
+acc +13
+acc -6
+acc -12
+nop +134
+jmp +345
+acc +5
+acc +16
+acc +35
+acc +50
+jmp +250
+acc +46
+jmp +105
+acc -6
+nop -152
+jmp +233
+jmp -88
+acc +39
+jmp +59
+acc -4
+acc +47
+jmp +165
+acc +32
+acc +49
+acc +24
+jmp +344
+acc -5
+acc +3
+jmp +359
+acc +27
+jmp +72
+acc +0
+acc +16
+acc +40
+jmp +98
+acc +2
+acc +23
+acc +48
+acc +2
+jmp -33
+jmp -186
+acc +27
+nop -83
+acc +2
+acc +19
+jmp -141
+acc +39
+acc +34
+acc +33
+jmp +282
+jmp +306
+acc +12
+jmp +317
+acc +32
+acc +50
+acc +17
+jmp +52
+acc +3
+acc +35
+jmp +328
+acc +26
+nop +163
+acc +6
+acc +19
+jmp +154
+acc +4
+jmp +1
+jmp +373
+acc -12
+acc +47
+jmp +1
+jmp -234
+acc +45
+acc +46
+acc -14
+acc +50
+jmp -134
+acc +26
+jmp +128
+jmp +233
+acc +23
+nop -133
+jmp -154
+jmp +260
+acc +21
+acc +14
+nop -89
+acc +9
+jmp -113
+acc +10
+acc +5
+jmp +127
+acc -9
+acc +2
+jmp +286
+nop +274
+jmp +93
+acc +46
+acc +36
+jmp +53
+acc +30
+jmp -126
+acc +11
+acc +11
+acc +23
+jmp +296
+nop -100
+jmp +304
+jmp +219
+acc +16
+jmp -93
+acc +12
+jmp +1
+jmp +205
+acc +6
+acc -11
+jmp +202
+jmp +107
+jmp +1
+jmp -224
+acc +24
+acc +50
+acc +37
+jmp +45
+acc +25
+acc -15
+jmp -151
+jmp +1
+acc +47
+jmp -196
+jmp +1
+jmp +300
+jmp +116
+acc +39
+acc +0
+nop -176
+acc -7
+jmp -53
+acc +20
+nop -216
+nop +291
+jmp +38
+acc +0
+acc +32
+acc -19
+jmp -28
+jmp -176
+acc +33
+acc +11
+acc +47
+nop -58
+jmp -203
+acc +48
+acc +50
+acc +41
+jmp -315
+acc -12
+acc +23
+acc +32
+jmp +210
+acc +46
+acc -11
+acc -16
+jmp +103
+acc +25
+nop +95
+acc +9
+jmp -117
+nop +18
+acc -19
+acc +38
+jmp -130
+acc +22
+jmp +25
+nop +201
+nop +205
+acc +14
+jmp -124
+jmp -46
+acc +9
+jmp -257
+acc -19
+acc -17
+acc +36
+acc +24
+jmp -210
+jmp -231
+acc +40
+jmp +46
+nop -192
+acc -13
+acc +7
+acc +33
+jmp +103
+acc +18
+acc +37
+acc -14
+jmp -11
+acc +12
+nop -240
+acc +35
+acc +33
+jmp -274
+acc -9
+acc +24
+jmp -128
+nop -129
+acc -17
+jmp -62
+acc +0
+acc +42
+nop +116
+jmp -44
+acc +16
+jmp +179
+acc -8
+acc +8
+jmp -149
+acc +39
+acc +2
+acc +14
+acc +12
+jmp -373
+jmp +76
+jmp -232
+jmp -385
+acc +22
+acc +41
+acc +28
+jmp -179
+acc +0
+acc +22
+acc +15
+jmp -291
+acc -18
+jmp -222
+acc +45
+acc -15
+jmp +61
+acc +10
+acc +16
+acc +43
+jmp +177
+acc +43
+acc -12
+acc +20
+acc +27
+jmp -13
+acc -14
+jmp -336
+nop -158
+acc +3
+nop -409
+acc +17
+jmp -257
+acc +0
+nop +124
+jmp +1
+jmp +117
+jmp -179
+acc -17
+acc -2
+jmp +1
+jmp -37
+acc +42
+jmp +175
+acc -9
+acc +12
+acc +4
+jmp +69
+acc -7
+jmp +1
+acc +32
+jmp +54
+jmp -444
+acc +7
+jmp -87
+acc -6
+nop -323
+acc +47
+acc -5
+jmp -143
+jmp +1
+nop -44
+acc +27
+acc +21
+jmp -184
+jmp -404
+jmp -70
+acc +32
+jmp -13
+acc +0
+nop -452
+acc +1
+acc +31
+jmp -77
+jmp -401
+acc +42
+jmp -428
+nop -120
+acc -17
+nop -75
+acc +6
+jmp +20
+jmp -291
+acc +7
+jmp +37
+acc +10
+acc +15
+jmp +1
+acc +11
+jmp -363
+acc -14
+nop -321
+jmp -40
+acc +41
+acc +31
+jmp +58
+jmp -493
+acc +32
+acc -10
+acc +44
+jmp -211
+acc +47
+acc +23
+jmp -241
+jmp -224
+acc -1
+jmp -350
+acc +8
+jmp -280
+acc -19
+acc +0
+acc +17
+jmp -274
+acc +27
+acc +11
+jmp -82
+acc +48
+acc +27
+jmp -518
+acc +3
+jmp -124
+jmp +1
+jmp -490
+acc +41
+jmp -238
+acc -6
+jmp -386
+jmp -189
+acc -11
+jmp +80
+acc -8
+acc +9
+nop -99
+jmp +56
+acc -18
+jmp -83
+acc +28
+acc +13
+jmp -228
+acc +32
+acc +34
+acc +3
+jmp -272
+nop -410
+acc +13
+acc -17
+jmp -236
+acc +45
+acc +0
+acc +19
+nop +29
+jmp +38
+jmp -75
+acc +7
+acc +33
+acc +40
+jmp -180
+jmp -557
+acc +22
+jmp -249
+acc +44
+acc +45
+acc +2
+acc -19
+jmp -537
+acc +44
+acc +32
+acc -14
+acc +39
+jmp -406
+jmp -488
+acc +14
+acc +41
+jmp -327
+acc +17
+acc +25
+nop -573
+acc +0
+jmp -563
+acc +18
+nop -282
+acc +13
+acc +45
+jmp -325
+acc +41
+acc -10
+nop -47
+nop -223
+jmp -155
+acc +14
+acc +23
+jmp +23
+acc +21
+nop -229
+acc +27
+acc -5
+jmp -95
+acc +2
+acc -10
+nop -451
+jmp -393
+jmp -406
+acc +42
+acc +18
+acc +49
+jmp -307
+acc -11
+jmp +1
+jmp -424
+jmp -192
+acc +49
+acc -1
+acc -17
+jmp -355
+jmp -268
+nop -320
+acc +1
+jmp -134
+acc +46
+jmp -564
+acc +40
+acc +29
+acc +13
+nop -285
+jmp -272
+acc +19
+acc -14
+acc +25
+acc +18
+jmp +1
diff --git a/2020/08-Handheld_Halting/second.hs b/2020/08-Handheld_Halting/second.hs
new file mode 100644
index 0000000..3396718
--- /dev/null
+++ b/2020/08-Handheld_Halting/second.hs
@@ -0,0 +1,67 @@
+-- requires cabal install --lib megaparsec parser-combinators
+module Main (main) where
+import Control.Monad (void, when)
+import Data.Maybe (fromJust)
+import qualified Data.Set as S
+import Data.Void (Void)
+import Text.Megaparsec
+import Text.Megaparsec.Char
+import System.Exit (die)
+
+exampleExpectedOutput = 8
+
+data Op = Nop Int | Acc Int | Jmp Int
+
+type Parser = Parsec Void String
+
+parseOp :: Parser Op
+parseOp = do
+  op <- string "nop " <|> string "acc " <|> string "jmp "
+  sign <- (char '+' *> return 1) <|> (char '-' *> return (-1))
+  num <- some digitChar
+  void $ char '\n'
+  let n = sign * (read num)
+  return $ case op of
+    "nop " -> Nop n
+    "acc " -> Acc n
+    "jmp " -> Jmp n
+
+parseOps :: Parser [Op]
+parseOps = some parseOp <* eof
+
+parseInput :: String -> IO [Op]
+parseInput filename = do
+  input <- readFile filename
+  case runParser parseOps filename input of
+    Left bundle -> die $ errorBundlePretty bundle
+    Right ops -> return ops
+
+run :: [Op] -> Int -> Int -> S.Set Int -> Bool -> Maybe Int
+run ops pointer acc visited mut
+  | pointer == last = Just acc
+  | S.member pointer visited = Nothing
+  | otherwise = case ops !! pointer of
+      Nop i -> case runNop mut of
+        Nothing -> if mut then Nothing else runJmp i True
+        Just n -> Just n
+      Acc i -> runAcc i mut
+      Jmp i -> case runJmp i mut of
+        Nothing -> if mut then Nothing else runNop True
+        Just n -> Just n
+  where
+    last = length ops
+    runAcc i = run ops (pointer + 1) (acc + i) visited'
+    runJmp i = run ops (pointer + i) acc visited'
+    runNop = run ops (pointer + 1) acc visited'
+    visited' = S.insert pointer visited
+
+compute :: [Op] -> Int
+compute ops = fromJust $ run ops 0 0 S.empty False
+
+main :: IO ()
+main = do
+  example <- parseInput "example"
+  let exampleOutput = compute example
+  when  (exampleOutput /= exampleExpectedOutput)  (die $ "example failed: got " ++ show exampleOutput ++ " instead of " ++ show exampleExpectedOutput)
+  input <- parseInput "input"
+  print $ compute input