Adding Haskell examples (#17)

* Adding binary search example for Haskell

* Adding selection sort example in Haskell

* Adding Haskell examples for chapter 3

* Adding examples for chapter 4

* Adding examples for chapter 5

* Adding git ignore

* Add Haskell example for BFS

01_introduction_to_algorithms/Haskell/01_binarysearch.hs

@@ -0,0 +1,21 @@
+import Data.Array
+
+binarysearch :: Integer -> Array Integer Integer -> Integer -> Integer -> Maybe Integer
+binarysearch x arr low high
+  | low > high = Nothing
+  | mid > x = binarysearch x arr low (high - 1)
+  | mid < x = binarysearch x arr (low + 1) high
+  | otherwise = Just mid
+  where
+    mid = arr ! ((low + high) `div` 2)
+
+
+find :: Integer -> Array Integer Integer -> Maybe Integer
+find x arr = binarysearch x arr low high
+  where p = bounds arr
+        low = fst p
+        high = snd p
+
+-- Usage
+-- let arr = array (0, 4) [(i, i*i) | i <- [0..4]]
+-- find 4 arr