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-rw-r--r--2020/02-Password_Philosophy/example3
-rw-r--r--2020/02-Password_Philosophy/first.hs59
-rw-r--r--2020/02-Password_Philosophy/input1000
-rw-r--r--2020/02-Password_Philosophy/second.hs60
4 files changed, 1122 insertions, 0 deletions
diff --git a/2020/02-Password_Philosophy/example b/2020/02-Password_Philosophy/example
new file mode 100644
index 0000000..fe19c03
--- /dev/null
+++ b/2020/02-Password_Philosophy/example
@@ -0,0 +1,3 @@
+1-3 a: abcde
+1-3 b: cdefg
+2-9 c: ccccccccc
diff --git a/2020/02-Password_Philosophy/first.hs b/2020/02-Password_Philosophy/first.hs
new file mode 100644
index 0000000..85c092e
--- /dev/null
+++ b/2020/02-Password_Philosophy/first.hs
@@ -0,0 +1,59 @@
+-- requires cabal install --lib megaparsec
+module Main (main) where
+
+import Control.Monad (void, when)
+import Data.Void
+import Text.Megaparsec
+import Text.Megaparsec.Char
+import System.Exit (die)
+
+exampleExpectedOutput = 2
+
+data Rule = Rule { lower :: Int
+ , higher :: Int
+ , elt :: Char
+ , pass :: String
+ } deriving (Show)
+
+type Parser = Parsec Void String
+
+parseRule :: Parser Rule
+parseRule = do
+ l <- try (some digitChar)
+ void (char '-')
+ h <- try (some digitChar)
+ void (char ' ')
+ e <- anySingle
+ void (string ": ")
+ pass <- (many letterChar)
+ void (char '\n')
+ return Rule { lower = read l, higher = read h, elt = e, pass = pass }
+
+parseRules :: Parser [Rule]
+parseRules = do
+ rules <- many parseRule
+ eof
+ return rules
+
+parseInput :: String -> IO [Rule]
+parseInput filename = do
+ input <- readFile filename
+ case runParser parseRules filename input of
+ Left bundle -> die $ errorBundlePretty bundle
+ Right rules -> return rules
+
+validateRule :: Rule -> Int
+validateRule Rule{lower=l, higher=h, elt=e, pass=pass} = if (n >= l && n <= h) then 1 else 0
+ where
+ n = length $ filter (== e) pass
+
+compute :: [Rule] -> Int
+compute = sum . map validateRule
+
+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/2020/02-Password_Philosophy/input b/2020/02-Password_Philosophy/input
new file mode 100644
index 0000000..5839a98
--- /dev/null
+++ b/2020/02-Password_Philosophy/input
@@ -0,0 +1,1000 @@
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+3-4 h: hrht
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+5-7 g: pmtgqgg
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diff --git a/2020/02-Password_Philosophy/second.hs b/2020/02-Password_Philosophy/second.hs
new file mode 100644
index 0000000..973a818
--- /dev/null
+++ b/2020/02-Password_Philosophy/second.hs
@@ -0,0 +1,60 @@
+-- requires cabal install --lib megaparsec
+module Main (main) where
+
+import Control.Monad (void, when)
+import Data.Void
+import Text.Megaparsec
+import Text.Megaparsec.Char
+import System.Exit (die)
+
+exampleExpectedOutput = 1
+
+data Rule = Rule { lower :: Int
+ , higher :: Int
+ , elt :: Char
+ , pass :: String
+ } deriving (Show)
+
+type Parser = Parsec Void String
+
+parseRule :: Parser Rule
+parseRule = do
+ l <- try (some digitChar)
+ void (char '-')
+ h <- try (some digitChar)
+ void (char ' ')
+ e <- anySingle
+ void (string ": ")
+ pass <- (many letterChar)
+ void (char '\n')
+ return Rule { lower = (read l) - 1, higher = (read h) - 1, elt = e, pass = pass }
+
+parseRules :: Parser [Rule]
+parseRules = do
+ rules <- many parseRule
+ eof
+ return rules
+
+parseInput :: String -> IO [Rule]
+parseInput filename = do
+ input <- readFile filename
+ case runParser parseRules filename input of
+ Left bundle -> die $ errorBundlePretty bundle
+ Right rules -> return rules
+
+validateRule :: Rule -> Int
+validateRule Rule{lower=l, higher=h, elt=e, pass=pass} = if (a /= b) then 1 else 0
+ where
+ a = e == pass !! l
+ b = e == pass !! h
+
+compute :: [Rule] -> Int
+compute = sum . map validateRule
+
+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