add 1.3 replace spaces

Author: cd155

src/Array.hs

@@ -1,5 +1,6 @@
 module Array where
 import Data.Map (Map, insert, member, adjust, empty)
+import Data.Char (ord)
 
 {-
     1.1
@@ -45,11 +46,45 @@ isUniqBFHelper c (x:xs) = (c /= x) && isUniqBFHelper c xs
     the set with the other.
 -}
 
+-- dictionary comparison
 isPerm :: String -> String -> Bool
 isPerm xs ys = convToDict xs empty == convToDict ys empty
 
-convToDict :: String -> Map Char Int -> Map Char Int
+convToDict :: String -> Map Char Integer -> Map Char Integer
 convToDict [] dict = dict
 convToDict (x:xs) dict
     | x `member` dict = convToDict xs (adjust (1+) x dict)
     | otherwise = convToDict xs (insert x 1 dict)
+
+-- ASCII array comparison
+-- initialize 128 ASCII array
+acciiArr = replicate 128 0
+
+isPerm' :: String -> String -> Bool
+isPerm' xs ys = fillAccii xs acciiArr == fillAccii ys acciiArr
+
+fillAccii :: String -> [Integer] -> [Integer]
+fillAccii [] arr = arr
+fillAccii (x:xs) arr = 
+    fillAccii xs (init firstHalf ++ [updated] ++ secondHalf)
+    where (firstHalf, secondHalf) = splitAt (ord x) arr
+          updated = (arr !! (ord x - 1)) + 1
+
+{-
+    1.3
+    Write a method to replace all spaces in a string with '%20'. 
+    You may assume that the string has sufficient space at the 
+    end to hold the additional characters,and that you are given 
+    the "true" length of the string.
+-}
+-- replace spaces with 20%, need to remove head(20%) and tail(20%)
+repSpace :: String -> String
+repSpace xs = repSpaceHelper xs False
+
+repSpaceHelper :: String -> Bool -> String
+repSpaceHelper [] _ = []
+repSpaceHelper (x:xs) isSpaPre
+    | x == ' ' && (not isSpaPre) = "20%" ++ repSpaceHelper xs (not isSpaPre)
+    | x == ' ' && isSpaPre = repSpaceHelper xs isSpaPre
+    | otherwise = x:repSpaceHelper xs False
+