第13回オフラインリアルタイムどう書くの参考問題をFregeで解く ref: http://qiita.com/uehaj/items/944cd9903c3827f1d1bc

shortest.fr

shortestPath' :: Int -> Int -> Int
shortestPath' n maxn
  | n==0 = 0
  | n==1 = 1
  | n > maxn = maxBound::Int
  | even(n) = (shortestPath' (n `div` 2) (maxn-2)) + 1
  | otherwise = minimum [(shortestPath' (n-1) (maxn-2)) + 1, (shortestPath' (n+1) (maxn-2)) + 1]

shortestPath :: Int -> Int  
shortestPath n = shortestPath' n (n*2)


main args = do
  println (shortestPath 59 ==  9)
  println (shortestPath 10 ==  5)
  println (shortestPath 11 ==  6)
  println (shortestPath 12 ==  5)
  println (shortestPath 13 ==  6)
  println (shortestPath 14 ==  6)
  println (shortestPath 15 ==  6)
  println (shortestPath 16 ==  5)
  println (shortestPath 17 ==  6)
  println (shortestPath 18 ==  6)
  println (shortestPath 27 ==  8)
  println (shortestPath 28 ==  7)
  println (shortestPath 29 ==  8)
  println (shortestPath 30 ==  7)
  println (shortestPath 31 ==  7)
  println (shortestPath 32 ==  6)
  println (shortestPath 33 ==  7)
  println (shortestPath 34 ==  7)
  println (shortestPath 35 ==  8)
  println (shortestPath 41 ==  8)
  println (shortestPath 71 ==  9)
  println (shortestPath 1023 ==  12)
  println (shortestPath 1024 ==  11)
  println (shortestPath 1025 ==  12)
  println (shortestPath 1707 ==  17)
  println (shortestPath 683 ==  15)
  println (shortestPath 123 ==  10)
  println (shortestPath 187 ==  11)
  println (shortestPath 237 ==  12)
  println (shortestPath 5267 ==  18)
  println (shortestPath 6737 ==  18)
  println (shortestPath 14796 ==  20)
  println (shortestPath 18998 ==  20)
  println (shortestPath 23820 ==  20)
  println (shortestPath 30380 ==  21)
  println (shortestPath 31119 ==  21)
  println (shortestPath 33301 ==  20)
  println (shortestPath 33967 ==  21)
  println (shortestPath 35443 ==  22)
  println (shortestPath 35641 ==  22)
  println (shortestPath 43695 ==  23)
  println (shortestPath 44395 ==  23)
  println (shortestPath 44666 ==  22)
  println (shortestPath 987 ==  14)
  println (shortestPath 1021 ==  13)
  println (shortestPath 1019 ==  13)
  println (shortestPath 1015 ==  13)
  println (shortestPath 1007 ==  13)
  println (shortestPath 1011 ==  14)
  println (shortestPath 1003 ==  14)
  println (shortestPath 983 ==  14)
  println (shortestPath 999 ==  14)
  println (shortestPath 2731 ==  18)
  println (shortestPath 6827 ==  20)
  println (shortestPath 10923 ==  21)
  println (shortestPath 27307 ==  23)
  println (shortestPath 43691 ==  24)
  println (shortestPath 109227 ==  26)
  println (shortestPath 174763 ==  27)