finish vol 3

1 files changed, 16 insertions, 0 deletions

diff --git a/21-28/28.hs b/21-28/28.hs
new file mode 100644
index 0000000..dd9270d
--- /dev/null
+++ b/21-28/28.hs
@@ -0,0 +1,16 @@
+import Data.List (sortBy, foldl', groupBy)
+import Data.Ord (comparing)
+
+lsort :: [[a]] -> [[a]]
+
+lsort = sortBy (comparing length)
+
+lfsort :: [[a]] -> [[a]]
+
+lfsort l =
+    [a | (a, b) <- sortBy (\x y -> (snd x) `compare` (snd y)) zipped]
+    where larr = map length l
+          count l e = foldl' (\acc x -> acc + (if x == e then 1 else 0)) 0 l
+          zipped = zip l (map (count larr) larr)
+
+lfsort2 = concat . lsort . groupBy (\x y -> length x == length y) . lsort