added magic square

willdoescode · willdoescode · commit 54fc54579735 · 2021-01-31T11:24:11.000-08:00
diff --git a/README.md b/README.md
@@ -18,5 +18,6 @@
 #### Medium
 
 * Sort List
+* [Magic Square](https://www.hackerrank.com/challenges/magic-square-forming/problem?h_r=internal-search)
 
 #### Hard
diff --git a/haskell-things.cabal b/haskell-things.cabal
@@ -30,3 +30,4 @@ executable haskell-things
                        , ToLowerCase
                        , MinimumIndexSumofTwoLists
                        , SortList
+                       , MagicSquare
diff --git a/haskell-things.iml b/haskell-things.iml
@@ -12,9 +12,10 @@
     <orderEntry type="sourceFolder" forTests="false" />
     <orderEntry type="library" name="base-4.13.0.0" level="project" />
     <orderEntry type="library" name="ghc-prim-0.5.3" level="project" />
-    <orderEntry type="library" name="integer-gmp-1.0.2.0" level="project" />
     <orderEntry type="library" name="containers-0.6.2.1" level="project" />
     <orderEntry type="library" name="array-0.5.4.0" level="project" />
     <orderEntry type="library" name="deepseq-1.4.4.0" level="project" />
+    <orderEntry type="library" name="base-4.14.1.0" level="project" />
+    <orderEntry type="library" name="integer-gmp-1.0.3.0" level="project" />
   </component>
 </module>
diff --git a/src/Main.hs b/src/Main.hs
@@ -10,6 +10,7 @@ import SortArrayByParity
 import ToLowerCase
 import MinimumIndexSumofTwoLists
 import SortList
+import MagicSquare
 
 main :: IO ()
 main = do
@@ -57,3 +58,11 @@ main = do
   print $ sortList ([9, 3, 4, 1] :: [Int]) -- cast types for no ide warning
   print $ (sortList . reverse . take 10) ([0..] :: [Int]) -- cast types for no ide warning
   print $ sortList ['c', 'a', 'f', 'y']
+
+  putStrLn "<-- Magic Square -->"
+  print $ magicSquare [ [4, 9, 2]
+                      , [3, 5, 7]
+                      , [8, 1, 5] ]
+  print $ magicSquare [ [4, 8, 2]
+                      , [4, 5, 7]
+                      , [6, 1, 6] ]
diff --git a/src/Medium/MagicSquare.hs b/src/Medium/MagicSquare.hs
@@ -0,0 +1,27 @@
+module MagicSquare ( magicSquare ) where
+
+-- https://www.hackerrank.com/challenges/magic-square-forming/problem?h_r=internal-search
+
+import Data.List
+
+type Square = [[Int]]
+
+magic :: Square
+magic = [ [8, 1, 6]
+        , [3, 5, 7]
+        , [4, 9, 2] ]
+
+rot90 :: Square -> Square
+rot90 = map reverse . transpose
+
+refl :: Square -> Square
+refl = transpose
+
+allMagic :: [Square]
+allMagic = take 4 (iterate rot90 magic) ++ take 4 (iterate rot90 $ refl magic)
+
+distance :: Square -> Square -> Int
+distance s1 s2 = sum $ map abs $ zipWith (-) (concat s1) (concat s2)
+
+magicSquare :: Square -> Int
+magicSquare s = minimum $ map (distance s) allMagic
diff --git a/src/Medium/SortList.hs b/src/Medium/SortList.hs
@@ -1,7 +1,7 @@
 module SortList ( sortList ) where
 
 -- Quick Sort
-  
+
 sortList :: (Ord a) => [a] -> [a]
 sortList (x:xs) = sortList [y | y <- xs, y <= x] ++ [x] ++ sortList [y | y <- xs, y > x]
 sortList [] = []
