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  1. Prepare
  2. Functional Programming
  3. Introduction
  4. Compute the Perimeter of a Polygon
  5. Discussions

Compute the Perimeter of a Polygon

  • Elmex90s
     + 1 comment

    My Haskell solution. Not the shortest, but very readable I hope.

    perimeter ls = sum [distance p q | (p, q) <- (zipW . makeCircular . zipV) ls]


distance :: (Int, Int) -> (Int, Int) -> Double
distance (x, y) (u, v) = sqrt (fromIntegral ((x - u)^2 + (y - v)^2)) 


zipV :: [a] -> [(a, a)]
zipV [] = []
zipV (x:y:ls) = ((x, y):(zipV ls))


zipW :: [a] -> [(a, a)]
zipW (x:ls) = zip (x:ls) ls


makeCircular :: [a] -> [a]
makeCircular ls = [last ls] ++ ls


main :: IO ()
main = do
    _ <- getLine
    x <- getContents
    let f = map (read::String->Int) $ words x
    print (perimeter f)