[New Exercise]: parallel letter frequency (#427)

* [New Exercise]: Parallel Letter Frequency

Add exercise `parallel letter frequency`

* Update config.json

Change difficulty

Author: glaxxie

config.json

@@ -615,14 +615,22 @@
         "prerequisites": [],
         "difficulty": 2
       },
-            {
+      {
         "slug": "line-up",
         "name": "Line Up",
         "uuid": "35d96adf-0fc2-4442-9299-76d880a70b3c",
         "practices": [],
         "prerequisites": [],
         "difficulty": 2
       },
+      {
+        "slug": "parallel-letter-frequency",
+        "name": "Parallel Letter Frequency",
+        "uuid": "6382ecca-b108-4fae-9901-dc1a9591a9cb",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 3
+      },
       {
         "slug": "error-handling",
         "name": "Error Handling",

exercises/practice/parallel-letter-frequency/.docs/instructions.md

@@ -0,0 +1,7 @@
+# Instructions
+
+Count the frequency of letters in texts using parallel computation.
+
+Parallelism is about doing things in parallel that can also be done sequentially.
+A common example is counting the frequency of letters.
+Employ parallelism to calculate the total frequency of each letter in a list of texts.

exercises/practice/parallel-letter-frequency/.meta/ParallelLetterFrequency.example.ps1

@@ -0,0 +1,27 @@
+Function Get-LetterFrequencies() {
+    <#
+    .SYNOPSIS
+    Count the frequency of letters in texts using parallel computation.
+
+    .PARAMETER Texts
+    An array of strings.
+    #>
+    [CmdletBinding()]
+    Param(
+        [string[]]$Texts
+    )
+    $final = @{}
+    $Texts | ForEach-Object -Parallel  {
+        $local = @{}
+        foreach ($ch in $_.ToLower().ToCharArray()) {
+            if ($ch -match '\p{L}') {
+                $local[$ch] = 1 + ($local[$ch] ?? 0)
+            }
+        }
+        $local} | ForEach-Object {
+        foreach ($k in $_.Keys) {
+            $final[[string]$k] = ($final[[string]$k] ?? 0) + $_[$k]
+        }
+    }
+   $final
+}

exercises/practice/parallel-letter-frequency/.meta/config.json

@@ -0,0 +1,17 @@
+{
+  "authors": [
+    "glaxxie"
+  ],
+  "files": {
+    "solution": [
+      "ParallelLetterFrequency.ps1"
+    ],
+    "test": [
+      "ParallelLetterFrequency.tests.ps1"
+    ],
+    "example": [
+      ".meta/ParallelLetterFrequency.example.ps1"
+    ]
+  },
+  "blurb": "Count the frequency of letters in texts using parallel computation."
+}

exercises/practice/parallel-letter-frequency/.meta/tests.toml

@@ -0,0 +1,49 @@
+# This is an auto-generated file.
+#
+# Regenerating this file via `configlet sync` will:
+# - Recreate every `description` key/value pair
+# - Recreate every `reimplements` key/value pair, where they exist in problem-specifications
+# - Remove any `include = true` key/value pair (an omitted `include` key implies inclusion)
+# - Preserve any other key/value pair
+#
+# As user-added comments (using the # character) will be removed when this file
+# is regenerated, comments can be added via a `comment` key.
+
+[c054d642-c1fa-4234-8007-9339f2337886]
+description = "no texts"
+
+[818031be-49dc-4675-b2f9-c4047f638a2a]
+description = "one text with one letter"
+
+[c0b81d1b-940d-4cea-9f49-8445c69c17ae]
+description = "one text with multiple letters"
+
+[708ff1e0-f14a-43fd-adb5-e76750dcf108]
+description = "two texts with one letter"
+
+[1b5c28bb-4619-4c9d-8db9-a4bb9c3bdca0]
+description = "two texts with multiple letters"
+
+[6366e2b8-b84c-4334-a047-03a00a656d63]
+description = "ignore letter casing"
+
+[92ebcbb0-9181-4421-a784-f6f5aa79f75b]
+description = "ignore whitespace"
+
+[bc5f4203-00ce-4acc-a5fa-f7b865376fd9]
+description = "ignore punctuation"
+
+[68032b8b-346b-4389-a380-e397618f6831]
+description = "ignore numbers"
+
+[aa9f97ac-3961-4af1-88e7-6efed1bfddfd]
+description = "Unicode letters"
+
+[7b1da046-701b-41fc-813e-dcfb5ee51813]
+description = "combination of lower- and uppercase letters, punctuation and white space"
+
+[4727f020-df62-4dcf-99b2-a6e58319cb4f]
+description = "large texts"
+
+[adf8e57b-8e54-4483-b6b8-8b32c115884c]
+description = "many small texts"

exercises/practice/parallel-letter-frequency/ParallelLetterFrequency.ps1

@@ -0,0 +1,15 @@
+Function Get-LetterFrequencies() {
+    <#
+    .SYNOPSIS
+    Count the frequency of letters in texts using parallel computation.
+
+    .PARAMETER Texts
+    An array of strings.
+    #>
+    [CmdletBinding()]
+    Param(
+        [string[]]$Texts
+    )
+    
+    Throw "Please implement this function"
+}