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-rw-r--r--2020/12-Rain_Risk/example5
-rw-r--r--2020/12-Rain_Risk/first.hs89
-rw-r--r--2020/12-Rain_Risk/input774
-rw-r--r--2020/12-Rain_Risk/second.hs66
4 files changed, 934 insertions, 0 deletions
diff --git a/2020/12-Rain_Risk/example b/2020/12-Rain_Risk/example
new file mode 100644
index 0000000..d382291
--- /dev/null
+++ b/2020/12-Rain_Risk/example
@@ -0,0 +1,5 @@
+F10
+N3
+F7
+R90
+F11
diff --git a/2020/12-Rain_Risk/first.hs b/2020/12-Rain_Risk/first.hs
new file mode 100644
index 0000000..e4e204e
--- /dev/null
+++ b/2020/12-Rain_Risk/first.hs
@@ -0,0 +1,89 @@
+-- requires cabal install --lib megaparsec parser-combinators
+module Main (main) where
+import Control.Monad (void, when)
+import Data.List (foldl')
+import Data.Void (Void)
+import Text.Megaparsec
+import Text.Megaparsec.Char
+import System.Exit (die)
+
+exampleExpectedOutput = 25
+
+data Action = N | S | E | W | L | R | F
+data Heading = HN | HS | HE | HW
+data Op = Op Action Int
+
+type Parser = Parsec Void String
+
+parseOp :: Parser Op
+parseOp = do
+ action <- (char 'N' *> return N)
+ <|> (char 'S' *> return S)
+ <|> (char 'E' *> return E)
+ <|> (char 'W' *> return W)
+ <|> (char 'L' *> return L)
+ <|> (char 'R' *> return R)
+ <|> (char 'F' *> return F)
+ num <- some digitChar
+ void $ char '\n'
+ return $ Op action (read num)
+
+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 = (\(x, y, _) -> abs(x)+abs(y)) $ foldl' step (0, 0, HE) ops
+ where
+ step :: (Int, Int, Heading) -> Op -> (Int, Int, Heading)
+ step (x, y, h) (Op N i) = (x, y+i, h)
+ step (x, y, h) (Op S i) = (x, y-i, h)
+ step (x, y, h) (Op E i) = (x+i, y, h)
+ step (x, y, h) (Op W i) = (x-i, y, h)
+ step (x, y, HN) (Op F i) = (x, y+i, HN)
+ step (x, y, HS) (Op F i) = (x, y-i, HS)
+ step (x, y, HE) (Op F i) = (x+i, y, HE)
+ step (x, y, HW) (Op F i) = (x-i, y, HW)
+ step (x, y, h) (Op a i) = (x, y, turn h a i)
+ turn :: Heading -> Action -> Int -> Heading
+ turn h a i = turn' h a mi
+ where mi = (i `mod` 360) `div` 90
+ turn' HN L 1 = HW
+ turn' HN L 2 = HS
+ turn' HN L 3 = HE
+ turn' HS L 1 = HE
+ turn' HS L 2 = HN
+ turn' HS L 3 = HW
+ turn' HE L 1 = HN
+ turn' HE L 2 = HW
+ turn' HE L 3 = HS
+ turn' HW L 1 = HS
+ turn' HW L 2 = HE
+ turn' HW L 3 = HN
+ turn' HN R 1 = HE
+ turn' HN R 2 = HS
+ turn' HN R 3 = HW
+ turn' HS R 1 = HW
+ turn' HS R 2 = HN
+ turn' HS R 3 = HE
+ turn' HE R 1 = HS
+ turn' HE R 2 = HW
+ turn' HE R 3 = HN
+ turn' HW R 1 = HN
+ turn' HW R 2 = HE
+ turn' HW R 3 = HS
+ turn' h _ _ = h
+
+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/2020/12-Rain_Risk/input b/2020/12-Rain_Risk/input
new file mode 100644
index 0000000..ab0ccce
--- /dev/null
+++ b/2020/12-Rain_Risk/input
@@ -0,0 +1,774 @@
+E2
+F24
+F60
+N3
+E1
+R180
+F14
+L90
+N4
+W3
+F81
+R90
+F43
+R90
+F40
+S2
+F56
+L90
+E1
+S1
+R90
+F66
+L180
+W2
+F84
+R90
+E4
+F32
+E5
+R90
+F44
+E1
+R90
+E4
+L90
+N1
+W2
+R90
+E5
+L90
+F86
+L180
+S2
+R180
+E2
+F22
+R180
+F42
+L180
+S4
+W4
+N5
+R270
+F23
+N3
+F18
+E2
+N2
+S3
+W5
+R90
+E4
+S1
+R180
+S1
+F69
+W2
+F55
+E5
+S3
+E4
+N1
+R180
+E1
+S5
+W1
+S5
+L270
+F17
+R180
+N5
+F6
+S3
+R180
+F75
+S3
+F90
+W3
+F98
+N2
+F54
+E5
+S5
+F4
+E5
+R90
+N4
+L90
+E4
+N3
+F75
+E3
+S2
+F89
+E1
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+S3
+E2
+R270
+W4
+L90
+N5
+E4
+W3
+N1
+F37
+L90
+N5
+E3
+N3
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+R90
+F25
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+F47
+E1
+F86
+N5
+W1
+N2
+F35
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+W3
+S3
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+L180
+F1
+L90
+E4
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+F58
+N2
+F95
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+F60
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+N1
+W2
+L90
+N3
+F16
+S2
+R90
+F3
+R270
+F98
+S4
+W1
+S4
+F42
+S5
+N2
+E1
+N4
+E3
+R180
+W3
+R180
+N4
+F47
+N5
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+F55
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+F12
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+N1
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+F89
+S4
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+N2
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+W1
+R90
+F50
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+W4
+F79
+E3
+F19
+N4
+L270
+N5
+W3
+F48
+R90
+F36
+S5
+F100
+E3
+F55
+N3
+F16
+R180
+S5
+N3
+R180
+N1
+F8
+E5
+L90
+F21
+L90
+F80
+L90
+N5
+W5
+S5
+E5
+R90
+N4
+E1
+F20
+S3
+L90
+E1
+N4
+F16
+F26
+E1
+F75
+E1
+R90
+F69
+N1
+E3
+R90
+F62
+L180
+W4
+F80
+S5
+L90
+F90
+W5
+F40
+W1
+L90
+W1
+R180
+S2
+F65
+E2
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+E1
+F37
+E5
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+N3
+W4
+S5
+E3
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+F54
+N5
+L180
+S4
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+F88
+R180
+F46
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+E3
+F93
+S2
+E5
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+F15
+R90
+F28
+S2
+F61
+N5
+L90
+W3
+S5
+L90
+N1
+L90
+F41
+W4
+N3
+F4
+N3
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+W5
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+E3
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+N2
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+N1
+R90
+N2
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+E3
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+L90
+S4
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+F69
+N3
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+F80
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+N5
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+F27
+N2
+F22
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+F74
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+S3
+F64
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+E2
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+S1
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+N1
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+R90
+F64
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+N1
+F5
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+N3
+E3
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+S4
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+W4
+L90
+S3
+L90
+F66
+L90
+E1
+F71
+L270
+F42
+N1
+W1
+L90
+S4
+E3
+F41
+R180
+F68
+W5
+L90
+N5
+E5
+F96
+W3
+F90
+S1
+E1
+R90
+N3
+F38
+R90
+W3
+R90
+W1
+L90
+S5
+F76
+E3
+F36
+S1
+L180
+E1
+F22
+N1
+W1
+R270
+E4
+N5
+E3
+N3
+W2
+L180
+S2
+W5
+N4
+W5
+N3
+R90
+S2
+F45
+R90
+W2
+R90
+W3
+F75
+R180
+E4
+N1
+E4
+L90
+F59
+L90
+S2
+E2
+S2
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+E2
+R90
+F37
+E2
+S1
+S5
+F97
+W4
+N1
+F58
+S2
+F14
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+N1
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+N5
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+F68
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+N5
+E2
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+L90
+E3
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+F36
diff --git a/2020/12-Rain_Risk/second.hs b/2020/12-Rain_Risk/second.hs
new file mode 100644
index 0000000..c036def
--- /dev/null
+++ b/2020/12-Rain_Risk/second.hs
@@ -0,0 +1,66 @@
+-- requires cabal install --lib megaparsec parser-combinators
+module Main (main) where
+import Control.Monad (void, when)
+import Data.List (foldl')
+import Data.Void (Void)
+import Text.Megaparsec
+import Text.Megaparsec.Char
+import System.Exit (die)
+
+exampleExpectedOutput = 286
+
+data Action = N | S | E | W | L | R | F
+data Op = Op Action Int
+
+type Parser = Parsec Void String
+
+parseOp :: Parser Op
+parseOp = do
+ action <- (char 'N' *> return N)
+ <|> (char 'S' *> return S)
+ <|> (char 'E' *> return E)
+ <|> (char 'W' *> return W)
+ <|> (char 'L' *> return L)
+ <|> (char 'R' *> return R)
+ <|> (char 'F' *> return F)
+ num <- some digitChar
+ void $ char '\n'
+ return $ Op action (read num)
+
+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 = (\((x, y), _) -> abs(x)+abs(y)) $ foldl' step ((0, 0), (10, 1)) ops
+ where
+ step :: ((Int, Int), (Int, Int)) -> Op -> ((Int, Int), (Int, Int))
+ step (p, (wx, wy)) (Op N i) = (p, (wx, wy+i))
+ step (p, (wx, wy)) (Op S i) = (p, (wx, wy-i))
+ step (p, (wx, wy)) (Op E i) = (p, (wx+i, wy))
+ step (p, (wx, wy)) (Op W i) = (p, (wx-i, wy))
+ step ((x, y), (wx, wy)) (Op F i) = ((x+i*wx, y+i*wy), (wx, wy))
+ step (p, w) (Op a i) = (p, turn w a i)
+ turn :: (Int, Int) -> Action -> Int -> (Int, Int)
+ turn w a i = turn' w a mi
+ where mi = (i `mod` 360) `div` 90
+ turn' (wx, wy) L 1 = (-wy, wx)
+ turn' (wx, wy) _ 2 = (-wx, -wy)
+ turn' (wx, wy) L 3 = (wy, -wx)
+ turn' (wx, wy) R 1 = (wy, -wx)
+ turn' (wx, wy) R 3 = (-wy, wx)
+ turn' w _ _ = w
+
+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