Merge pull request #172 from seanyu4296/add-purescript-solution-for-chapter-1-chapter-2

Add purescript solution for chapter 1 chapter 2

01_introduction_to_algorithms/Purescript/BinarySearch.purs

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+module GrokkingAlgos.BinarySearch where
+
+import Prelude
+import Data.Array ((!!))
+import Data.Array as Array
+import Data.Maybe (Maybe(..))
+import Effect (Effect)
+import Effect.Class.Console (logShow)
+
+-- | Binary Search - input is a sorted list of elements
+-- | Big o notation - log n
+-- | Traveling salesman - O (n!)
+binarysearch :: Int -> Array Int -> Int -> Int -> Maybe Int
+binarysearch x arr low high
+  | low > high = Nothing
+  | otherwise =
+    let
+      mid = (high + low) / 2
+    in
+      arr !! mid
+        >>= case _ of
+            item
+              | item == x -> Just mid
+            item
+              | item > x -> binarysearch x arr low (mid - 1)
+            item
+              | item < x -> binarysearch x arr (mid + 1) high
+            _ -> Nothing
+
+find :: Int -> Array Int -> Maybe Int
+find x arr = binarysearch x arr low high
+  where
+  low = 0
+
+  high = (Array.length arr) - 1
+
+main :: Effect Unit
+main = do
+  logShow $ find 20 [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20 ]

01_introduction_to_algorithms/Purescript/README.md

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+# Getting Started
+1. Install `spago` and `purescript` through `yarn` or `npm` (e.g. `yarn global add spago` and `yarn global add purescript`)
+2. Run file through `spago run --watch --main <module-name>` (e.g. `spago run --watch --main GrokkingAlgos.SelectionSort`)
+
+# Main Repo
+- https://github.com/seanyu4296/grokking-algo-in-purs

01_introduction_to_algorithms/Purescript/packages.dhall

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+let upstream =
+      https://github.com/purescript/package-sets/releases/download/psc-0.13.8-20200724/packages.dhall sha256:bb941d30820a49345a0e88937094d2b9983d939c9fd3a46969b85ce44953d7d9
+
+let overrides = {=}
+
+let additions = {=}
+
+in  upstream // overrides // additions

01_introduction_to_algorithms/Purescript/spago.dhall

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+{-
+Welcome to a Spago project!
+You can edit this file as you like.
+-}
+{ name = "my-project"
+, dependencies = [ "console", "effect", "psci-support", "arrays", "debug", "lists", "ordered-collections", "strings"]
+, packages = ./packages.dhall
+, sources = [ "src/**/*.purs", "test/**/*.purs" ]
+}

02_selection_sort/Purescript/README.md

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+# Getting Started
+1. Install `spago` and `purescript` through `yarn` or `npm` (e.g. `yarn global add spago` and `yarn global add purescript`)
+2. Run file through `spago run --watch --main <module-name>` (e.g. `spago run --watch --main GrokkingAlgos.SelectionSort`)
+
+# Main Repo
+- https://github.com/seanyu4296/grokking-algo-in-purs

02_selection_sort/Purescript/SelectionSort.purs

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+module GrokkingAlgos.SelectionSort where
+
+import Prelude
+import Data.Foldable (minimum)
+import Data.List (List(..), delete, (:))
+import Data.Maybe (Maybe(..))
+import Effect (Effect)
+import Effect.Class.Console (logShow)
+
+selectionsort :: List Int -> List Int
+selectionsort l = case minimum l of
+  Nothing -> Nil
+  Just min -> min : selectionsort (delete min l)
+
+main :: Effect Unit
+main = do
+  logShow $ selectionsort $ 1 : 2 : 3 : 5 : 4 : Nil

02_selection_sort/Purescript/packages.dhall

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+let upstream =
+      https://github.com/purescript/package-sets/releases/download/psc-0.13.8-20200724/packages.dhall sha256:bb941d30820a49345a0e88937094d2b9983d939c9fd3a46969b85ce44953d7d9
+
+let overrides = {=}
+
+let additions = {=}
+
+in  upstream // overrides // additions

02_selection_sort/Purescript/spago.dhall

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+{-
+Welcome to a Spago project!
+You can edit this file as you like.
+-}
+{ name = "my-project"
+, dependencies = [ "console", "effect", "psci-support", "arrays", "debug", "lists", "ordered-collections", "strings"]
+, packages = ./packages.dhall
+, sources = [ "src/**/*.purs", "test/**/*.purs" ]
+}