Add purescript solution for chapt 1

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> GrokkingAlgos.SelectionSort` (e.g. `spago run --watch --main GrokkingAlgos.SelectionSort`)

01_introduction_to_algorithms/Purescript/packages.dhall

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+{-
+Welcome to your new Dhall package-set!
+
+Below are instructions for how to edit this file for most use
+cases, so that you don't need to know Dhall to use it.
+
+## Warning: Don't Move This Top-Level Comment!
+
+Due to how `dhall format` currently works, this comment's
+instructions cannot appear near corresponding sections below
+because `dhall format` will delete the comment. However,
+it will not delete a top-level comment like this one.
+
+## Use Cases
+
+Most will want to do one or both of these options:
+1. Override/Patch a package's dependency
+2. Add a package not already in the default package set
+
+This file will continue to work whether you use one or both options.
+Instructions for each option are explained below.
+
+### Overriding/Patching a package
+
+Purpose:
+- Change a package's dependency to a newer/older release than the
+    default package set's release
+- Use your own modified version of some dependency that may
+    include new API, changed API, removed API by
+    using your custom git repo of the library rather than
+    the package set's repo
+
+Syntax:
+Replace the overrides' "{=}" (an empty record) with the following idea
+The "//" or "⫽" means "merge these two records and
+  when they have the same value, use the one on the right:"
+-------------------------------
+let override =
+  { packageName =
+      upstream.packageName // { updateEntity1 = "new value", updateEntity2 = "new value" }
+  , packageName =
+      upstream.packageName // { version = "v4.0.0" }
+  , packageName =
+      upstream.packageName // { repo = "https://www.example.com/path/to/new/repo.git" }
+  }
+-------------------------------
+
+Example:
+-------------------------------
+let overrides =
+  { halogen =
+      upstream.halogen // { version = "master" }
+  , halogen-vdom =
+      upstream.halogen-vdom // { version = "v4.0.0" }
+  }
+-------------------------------
+
+### Additions
+
+Purpose:
+- Add packages that aren't already included in the default package set
+
+Syntax:
+Replace the additions' "{=}" (an empty record) with the following idea:
+-------------------------------
+let additions =
+  { package-name =
+       { dependencies =
+           [ "dependency1"
+           , "dependency2"
+           ]
+       , repo =
+           "https://example.com/path/to/git/repo.git"
+       , version =
+           "tag ('v4.0.0') or branch ('master')"
+       }
+  , package-name =
+       { dependencies =
+           [ "dependency1"
+           , "dependency2"
+           ]
+       , repo =
+           "https://example.com/path/to/git/repo.git"
+       , version =
+           "tag ('v4.0.0') or branch ('master')"
+       }
+  , etc.
+  }
+-------------------------------
+
+Example:
+-------------------------------
+let additions =
+  { benchotron =
+      { dependencies =
+          [ "arrays"
+          , "exists"
+          , "profunctor"
+          , "strings"
+          , "quickcheck"
+          , "lcg"
+          , "transformers"
+          , "foldable-traversable"
+          , "exceptions"
+          , "node-fs"
+          , "node-buffer"
+          , "node-readline"
+          , "datetime"
+          , "now"
+          ]
+      , repo =
+          "https://github.com/hdgarrood/purescript-benchotron.git"
+      , version =
+          "v7.0.0"
+      }
+  }
+-------------------------------
+-}
+
+
+let upstream =
+      https://github.com/purescript/package-sets/releases/download/psc-0.13.6-20200226/packages.dhall sha256:3a52562e05b31a7b51d12d5b228ccbe567c527781a88e9028ab42374ab55c0f1
+
+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" ]
+}