day fifteen

DayFifteen.hs

{-# LANGUAGE OverloadedStrings #-}
module DayFifteen
    ( main
    ) where
import qualified Data.Maybe as M
import qualified Data.Ord as O
import qualified Data.Text as T
import qualified Data.Text.IO as TI
import qualified Data.List as L
import qualified Data.List.Split as LS
import qualified Data.Set as S
import qualified Data.Function as F
import Data.Range
import Debug.Trace

data Coordinate = Coordinate { x :: Int, y :: Int } deriving (Eq, Ord, Show)
data InputFact = InputFact { sensor :: Coordinate, beacon :: Coordinate } deriving (Eq, Show)

distanceToRow coordinate row = manhattan coordinate (Coordinate (x coordinate) row)

radius InputFact { sensor, beacon } = manhattan sensor beacon

parse line = InputFact { sensor=(Coordinate sensorX sensorY), beacon=(Coordinate beaconX beaconY)}
  where splitted = T.split (`L.elem` splitters) line
        splitters :: String = ",=:"
        sensorX = readText (splitted !! 1)
        sensorY = readText (splitted !! 3)
        beaconX = readText (splitted !! 5)
        beaconY = readText (splitted !! 7)
        readText = read . T.unpack

manhattan Coordinate{x=fromX,y=fromY} Coordinate{x=toX,y=toY} = (abs (fromX - toX)) + (abs (fromY - toY))

testInput :: [T.Text]
testInput = [
  "Sensor at x=2, y=18: closest beacon is at x=-2, y=15",
  "Sensor at x=9, y=16: closest beacon is at x=10, y=16",
  "Sensor at x=13, y=2: closest beacon is at x=15, y=3",
  "Sensor at x=12, y=14: closest beacon is at x=10, y=16",
  "Sensor at x=10, y=20: closest beacon is at x=10, y=16",
  "Sensor at x=14, y=17: closest beacon is at x=10, y=16",
  "Sensor at x=8, y=7: closest beacon is at x=2, y=10",
  "Sensor at x=2, y=0: closest beacon is at x=2, y=10",
  "Sensor at x=0, y=11: closest beacon is at x=2, y=10",
  "Sensor at x=20, y=14: closest beacon is at x=25, y=17",
  "Sensor at x=17, y=20: closest beacon is at x=21, y=22",
  "Sensor at x=16, y=7: closest beacon is at x=15, y=3",
  "Sensor at x=14, y=3: closest beacon is at x=15, y=3",
  "Sensor at x=20, y=1: closest beacon is at x=15, y=3"
  ]

testFacts = map parse testInput
emptyRange = 1 *=* 1

getFootprintInTargetRow targetRow fact
  | relativeRadius >= 1 = low +=+ high
  | relativeRadius == 0 = SingletonRange (x theSensor)
  | otherwise = emptyRange
    where relativeRadius = (radius fact) - (distanceToRow theSensor targetRow)
          theSensor = sensor fact
          low = (x theSensor) - relativeRadius
          high = ((x theSensor) + relativeRadius)



main targetRow facts = S.size realAnswer
  where overcount = fromRanges $ mergeRanges $ map (getFootprintInTargetRow targetRow) facts
        overcountCoordinates = S.fromList $ map (\x -> (Coordinate x targetRow)) overcount
        realAnswer = S.difference overcountCoordinates beacons
        beacons = S.fromList $ map beacon facts


rowIsInteresting minX maxX facts targetRow = [wholeRange] /= (intersection wholeFootprint [wholeRange])
  where wholeRange = minX +=+ maxX
        wholeFootprint = joinRanges $ map (getFootprintInTargetRow targetRow) facts

partTwo facts minX maxX minY maxY = filter (rowIsInteresting minX maxX facts) [minY..maxY]

getLines path = do
  input <- TI.readFile path
  return $ T.lines input