55 lines
1.7 KiB
Haskell
55 lines
1.7 KiB
Haskell
|
-- main.hs as written by me, thuroughly fixed by <https://github.com/h7x4>
|
||
|
|
main :: IO ()
|
||
|
|
main = do
|
||
|
|
file <- readFile "input.txt"
|
||
|
|
let
|
||
|
|
pairs :: [((Int, Int), (Int, Int))]
|
||
|
|
pairs = inputLinesToPairs file
|
||
|
|
|
||
|
|
putStrLn "Part 1: "
|
||
|
|
print $ part1 pairs
|
||
|
|
|
||
|
|
putStrLn "Part 2: "
|
||
|
|
print $ part2 pairs
|
||
|
|
|
||
|
|
-- Map each line of input from "1-2,3-4" to ((1,2),(3,4))
|
||
|
|
inputLinesToPairs :: String -> [((Int, Int), (Int, Int))]
|
||
|
|
inputLinesToPairs input = result
|
||
|
|
where
|
||
|
|
stringpairs :: [[String]]
|
||
|
|
stringpairs = map (splitWhen (==',')) $ lines input
|
||
|
|
|
||
|
|
parseRange :: String -> (Int, Int)
|
||
|
|
parseRange pair = (read first, read second)
|
||
|
|
where
|
||
|
|
(first:second:_) = splitWhen (=='-') pair
|
||
|
|
|
||
|
|
result :: [((Int, Int), (Int, Int))]
|
||
|
|
result = map (\x -> (head x, last x)) $ map (map parseRange) stringpairs
|
||
|
|
|
||
|
|
|
||
|
|
part1 :: [((Int, Int), (Int, Int))] -> Int
|
||
|
|
part1 = length . filter (uncurry rangeIsContained)
|
||
|
|
|
||
|
|
part2 :: [((Int, Int), (Int, Int))] -> Int
|
||
|
|
part2 = length . filter (uncurry rangeOverlaps)
|
||
|
|
|
||
|
|
-- True if any part of the two ranges overlap
|
||
|
|
rangeOverlaps :: (Int, Int) -> (Int, Int) -> Bool
|
||
|
|
rangeOverlaps (lo1, hi1) (lo2, hi2) = rangeIsContained (lo1, lo1) (lo2, hi2)
|
||
|
|
|| (lo2 >= lo1 && lo2 <= hi1)
|
||
|
|
|| (hi2 >= lo1 && hi2 <= hi1)
|
||
|
|
|
||
|
|
-- True if the first range is entirely contained in the second range, or vice versa
|
||
|
|
rangeIsContained :: (Int, Int) -> (Int, Int) -> Bool
|
||
|
|
rangeIsContained (lo1, hi1) (lo2, hi2) = (lo1 <= lo2 && hi1 >= hi2)
|
||
|
|
|| (lo1 >= lo2 && hi1 <= hi2)
|
||
|
|
|
||
|
|
-- Modified from Prelude.words
|
||
|
|
splitWhen :: (Char -> Bool) -> String -> [String]
|
||
|
|
splitWhen p s = case dropWhile p s of
|
||
|
|
"" -> []
|
||
|
|
s' -> w : splitWhen p s''
|
||
|
|
where (w, s'') = break p s'
|
||
|
|
|