5kyu: add pick peaks

Signed-off-by: Matej Focko <mfocko@redhat.com>

5kyu/pick_peaks/solution.hs

@@ -0,0 +1,30 @@
+module PickPeak.JorgeVS.Kata where
+
+data PickedPeaks = PickedPeaks { pos :: [Int], peaks :: [Int] } deriving (Eq, Show)
+
+windowed :: Int -> [a] -> [[a]]
+windowed n xs
+  | null xs || length window < n = []
+  | otherwise = window : (windowed n $ tail xs)
+  where window = take n xs
+
+addIfPeak :: PickedPeaks -> [(Int, Int)] -> PickedPeaks
+addIfPeak ps [l, mid, r]
+  | (snd mid > snd l) && (snd mid > snd r) = PickedPeaks { pos = fst mid : pos ps, peaks = snd mid : peaks ps }
+  | otherwise = ps
+addIfPeak _ _ = error "Invalid state"
+
+removeConsecutiveDuplicates :: [(Int, Int)] -> [(Int, Int)]
+removeConsecutiveDuplicates = foldr addIfNotDuplicate []
+  where addIfNotDuplicate :: (Int, Int) -> [(Int, Int)] -> [(Int, Int)]
+        addIfNotDuplicate pair [] = [pair]
+        addIfNotDuplicate pair@(i, x) pairs
+          | x == (snd . head) pairs = pair : tail pairs
+          | otherwise = pair : pairs
+
+pickPeaks :: [Int] -> PickedPeaks
+pickPeaks = foldl addIfPeak PickedPeaks { pos = [], peaks = [] }
+          . windowed 3
+          . reverse
+          . removeConsecutiveDuplicates
+          . zip [0..]

README.md

@@ -97,6 +97,7 @@
 ### Haskell
 
 - [Directions Reduction](https://www.codewars.com/kata/550f22f4d758534c1100025a) - [solution](5kyu/directions_reduction)
+- [Pick peaks](https://www.codewars.com/kata/5279f6fe5ab7f447890006a7) - [solution](5kyu/pick_peaks)
 
 ### JS