mipt_ict/03_dijkstra/02_least_reachable_city/main.hs

module Main where

import System.IO 
import System.Environment

import qualified Data.Map as Map
import qualified Data.Set as Set

import LeastReachableCity
import Types

{- format of input file is:
 - mileage
 - from to len
 - from to len
 - ...
 - where "from" and "to" are numbers of graph vertices, "len" is distance between them
 - -}
main :: IO()
main = do
    argv <- getArgs

    filename <- if not $ null argv then do
        head <$> getArgs
    else do
        putStrLn "Usage: ./lrc [filename]\nNow defaulting to file \"data\""
        return "data"

    content <- readFile filename
    let mileage = read $ head $ lines content :: Len
    let graph = readGraph $ tail content
    let (city, n) = leastReachableCity graph mileage
    putStrLn $ "The least reachable city is " ++ (show city) ++ " (" ++ (show n) ++ " city/ies is/are reachable)"

{- For parsing graph using content of the file -} 
parseStrNode :: [String] -> Node
parseStrNode [a, b, c] = Node (p a, p b, l c) where
    p x = read x :: Point
    l x = read x :: Len

readGraph :: String -> Graph
readGraph content = parse lst where
            parse (x:xs) = if length ws == 3 then (parseStrNode ws) : (parse xs) else parse xs where
                ws = words x
            parse _ = [] 
            lst = lines content