add 1.1 isUnique

Author: cd155

src/Array.hs

@@ -0,0 +1,39 @@
+module Array where
+
+{-
+    1.1
+    Implement an algorithm to determine if a string has all unique 
+    characters. What if you cannot use additional data structures?
+-}
+isUniq :: Eq a => [a] -> Bool
+isUniq xs = isUniqHelper xs []
+
+isUniqHelper :: Eq a => [a] -> [a] -> Bool
+isUniqHelper [] _ = True
+isUniqHelper (x:xs) dict
+    | x `elem` dict = False
+    | otherwise = isUniqHelper xs (x:dict)
+
+-- check unique without structure
+isUniqBF :: Eq a => [a] -> Bool
+isUniqBF [] = True
+isUniqBF (x:xs) = isUniqBFHelper x xs && isUniqBF xs
+
+-- compare an element with a list
+isUniqBFHelper :: Eq a => a -> [a] -> Bool
+isUniqBFHelper _ [] = True
+isUniqBFHelper c (x:xs) = (c /= x) && isUniqBFHelper c xs
+
+{-
+    isUniqBF code animation:
+
+    r1:
+        abc
+        a bc => a /= b && a /= c
+
+    r2:
+        bc
+        b c => b /= c
+
+    final: r1 && r2
+-}