Day 4: Initial version

Now to look at other solutions

2019/day4/day4.hs

@@ -0,0 +1,28 @@
+import Data.List
+
+main = do
+    let bottom = 130254
+    let top = 678275
+    print (day4a bottom top)
+    print (day4b bottom top)
+
+day4a bottom top = dumbbrute bottom top p 0
+day4b bottom top = dumbbrute bottom top p' 0
+
+dumbbrute x y p acc
+    | x'<=y = dumbbrute x' y p (if p (numexpl x) then acc+1 else acc)
+    | otherwise = acc
+    where x' = succ x
+
+p x
+    | sort x /= x = False
+    | nub x == x = False
+    | otherwise = True
+
+p' x
+    | sort x /= x = False
+    | 2 `elem` (map length $ group x) = True
+    | otherwise = False
+
+numexpl 0 = []
+numexpl x = numexpl (x `div` 10) ++ [x `mod` 10]