Problem 81（Dijkstra)

Dijkstraで解く。

import Dijkstra
import Data.Graph
import Data.Array.IArray

w = 80
xi (i,j) = w*i+j

mkGraph = buildG (0,w*w).((w*w,0):).concatMap e$range b
    where b = ((0,0),(w-1,w-1))
          e (i,j) = [(xi (i,j),xi x)|x<-[(i+1,j),(i,j+1)],inRange b x]
mkWeight a = array b .(s:).concatMap e $range b'::Weight
    where b = ((0,0),(w*w,w*w))
          b' = ((0,0),(w-1,w-1))
          e (i,j) = [((xi (i,j),xi x),a!x)|x<-[(i+1,j),(i,j+1)],inRange b' x]
          s = ((w*w,0),a!(0,0))
mkArray ::String->Array (Int,Int) Int
mkArray ws= listArray ((0,0),(w-1,w-1)) ws'
    where ws'=concat.map (read.g).lines$ws 
          g x = "["++x++"]"

main =do
  f<-readFile "matrix.txt"
  print.fst.shortestPath mkGraph (mkWeight$mkArray f) (w*w) $w*w-1

DPのほうが速かった件について