- Added solutions by Eric Cheung.

- Added solutions by Richar Park.
- Added solutions by PokGoPun.
- Added solutions by Neils van Dijke.
- Added solutions by Mark Anderson.
- Added solutions by E. Choroba.
- Added solutions by Luca Ferrari.
- Added solutions by Peter Campbell Smith.
- Added solutions by Conor Hoekstra.
- Added solutions by David Ferrone.
- Added solutions by Robbie Hatley.
- Added solutions by W. Luis Mochan.
- Added solutions by Feng Chang.
- Added solutions by Roger Bell_West.

56 files changed, 3759 insertions, 3005 deletions

diff --git a/challenge-305/conor-hoekstra/ch-1.bqn b/challenge-305/conor-hoekstra/bqn/ch-1.bqn
index 311c35c960..311c35c960 100644
--- a/challenge-305/conor-hoekstra/ch-1.bqn
+++ b/challenge-305/conor-hoekstra/bqn/ch-1.bqn
diff --git a/challenge-305/conor-hoekstra/ch-2.bqn b/challenge-305/conor-hoekstra/bqn/ch-2.bqn
index 67b1ac5aa0..67b1ac5aa0 100644
--- a/challenge-305/conor-hoekstra/ch-2.bqn
+++ b/challenge-305/conor-hoekstra/bqn/ch-2.bqn
diff --git a/challenge-305/eric-cheung/python/ch-1.py b/challenge-305/eric-cheung/python/ch-1.py
new file mode 100755
index 0000000000..39344cda93
--- /dev/null
+++ b/challenge-305/eric-cheung/python/ch-1.py
@@ -0,0 +1,16 @@
+

+from sympy import isprime

+

+## arrBinary = [1,  0,  1]  ## Example 1

+## arrBinary = [1, 1, 0]  ## Example 2

+arrBinary = [1, 1, 1, 1, 0, 1, 0, 0, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 0, 1]  ## Example 3

+

+arrStrBinary = [str(nElem) for nElem in arrBinary]

+arrOutput = [False]

+

+## for nIndx in range(1, len(arrStrBinary)):

+    ## arrOutput.append(isprime(int("".join(arrStrBinary[ : nIndx + 1]), 2)))

+

+arrOutput = arrOutput + [isprime(int("".join(arrStrBinary[ : nIndx + 1]), 2)) for nIndx in range(1, len(arrStrBinary))]

+

+print (arrOutput)

diff --git a/challenge-305/eric-cheung/python/ch-2.py b/challenge-305/eric-cheung/python/ch-2.py
new file mode 100755
index 0000000000..91237db3ca
--- /dev/null
+++ b/challenge-305/eric-cheung/python/ch-2.py
@@ -0,0 +1,34 @@
+

+def IsStrGreater(strInput_01, strInput_02):

+    global arrAlien

+    if strInput_01 == strInput_02:

+        return False

+

+    nMinLen = min(len(strInput_01), len(strInput_02))

+

+    if strInput_01[:nMinLen] == strInput_02[:nMinLen]:

+        return len(strInput_01) > len(strInput_02)

+

+    for nIndx in range(nMinLen):

+        if strInput_01[nIndx] == strInput_02[nIndx]:

+            continue

+        return arrAlien.index(strInput_01[nIndx]) > arrAlien.index(strInput_02[nIndx])

+

+## Example 1

+## arrWords = ["perl", "python", "raku"]

+## arrAlien = ["h", "l", "a", "b", "y", "d", "e", "f", "g", "i", "r", "k", "m", "n", "o", "p", "q", "j", "s", "t", "u", "v", "w", "x", "c", "z"]

+

+## Example 2

+arrWords = ["the", "weekly", "challenge"]

+arrAlien = ["c", "o", "r", "l", "d", "a", "b", "t", "e", "f", "g", "h", "i", "j", "k", "m", "n", "p", "q", "s", "w", "u", "v", "x", "y", "z"]

+

+for nRowLoop in range(len(arrWords) - 1):

+    for nColLoop in range(nRowLoop + 1, len(arrWords)):

+        if not IsStrGreater(arrWords[nRowLoop], arrWords[nColLoop]):

+            continue

+

+        strTemp = arrWords[nRowLoop]

+        arrWords[nRowLoop] = arrWords[nColLoop]

+        arrWords[nColLoop] = strTemp

+

+print (arrWords)

diff --git a/challenge-306/luca-ferrari/blog-1.txt b/challenge-305/luca-ferrari/blog-1.txt
index a11f262a59..a11f262a59 100644
--- a/challenge-306/luca-ferrari/blog-1.txt
+++ b/challenge-305/luca-ferrari/blog-1.txt
diff --git a/challenge-306/luca-ferrari/blog-10.txt b/challenge-305/luca-ferrari/blog-10.txt
index efa146d6f9..efa146d6f9 100644
--- a/challenge-306/luca-ferrari/blog-10.txt
+++ b/challenge-305/luca-ferrari/blog-10.txt
diff --git a/challenge-306/luca-ferrari/blog-2.txt b/challenge-305/luca-ferrari/blog-2.txt
index 4b511d6565..4b511d6565 100644
--- a/challenge-306/luca-ferrari/blog-2.txt
+++ b/challenge-305/luca-ferrari/blog-2.txt
diff --git a/challenge-306/luca-ferrari/blog-3.txt b/challenge-305/luca-ferrari/blog-3.txt
index ff43738b0f..ff43738b0f 100644
--- a/challenge-306/luca-ferrari/blog-3.txt
+++ b/challenge-305/luca-ferrari/blog-3.txt
diff --git a/challenge-306/luca-ferrari/blog-4.txt b/challenge-305/luca-ferrari/blog-4.txt
index 94da3eec7e..94da3eec7e 100644
--- a/challenge-306/luca-ferrari/blog-4.txt
+++ b/challenge-305/luca-ferrari/blog-4.txt
diff --git a/challenge-306/luca-ferrari/blog-5.txt b/challenge-305/luca-ferrari/blog-5.txt
index f1f5420190..f1f5420190 100644
--- a/challenge-306/luca-ferrari/blog-5.txt
+++ b/challenge-305/luca-ferrari/blog-5.txt
diff --git a/challenge-306/luca-ferrari/blog-6.txt b/challenge-305/luca-ferrari/blog-6.txt
index a3c426291c..a3c426291c 100644
--- a/challenge-306/luca-ferrari/blog-6.txt
+++ b/challenge-305/luca-ferrari/blog-6.txt
diff --git a/challenge-306/luca-ferrari/blog-7.txt b/challenge-305/luca-ferrari/blog-7.txt
index 140cfd2d06..140cfd2d06 100644
--- a/challenge-306/luca-ferrari/blog-7.txt
+++ b/challenge-305/luca-ferrari/blog-7.txt
diff --git a/challenge-306/luca-ferrari/blog-8.txt b/challenge-305/luca-ferrari/blog-8.txt
index 330e58a7c1..330e58a7c1 100644
--- a/challenge-306/luca-ferrari/blog-8.txt
+++ b/challenge-305/luca-ferrari/blog-8.txt
diff --git a/challenge-306/luca-ferrari/blog-9.txt b/challenge-305/luca-ferrari/blog-9.txt
index 5c4a0e081f..5c4a0e081f 100644
--- a/challenge-306/luca-ferrari/blog-9.txt
+++ b/challenge-305/luca-ferrari/blog-9.txt
diff --git a/challenge-306/luca-ferrari/pljava/pom.xml b/challenge-305/luca-ferrari/pljava/pom.xml
index 99c9085d7e..99c9085d7e 100644
--- a/challenge-306/luca-ferrari/pljava/pom.xml
+++ b/challenge-305/luca-ferrari/pljava/pom.xml
diff --git a/challenge-306/luca-ferrari/pljava/src/main/java/Task1.java b/challenge-305/luca-ferrari/pljava/src/main/java/Task1.java
index d2e48bcd52..d2e48bcd52 100644
--- a/challenge-306/luca-ferrari/pljava/src/main/java/Task1.java
+++ b/challenge-305/luca-ferrari/pljava/src/main/java/Task1.java
diff --git a/challenge-306/luca-ferrari/pljava/src/main/java/Task2.java b/challenge-305/luca-ferrari/pljava/src/main/java/Task2.java
index bd365bdaba..bd365bdaba 100644
--- a/challenge-306/luca-ferrari/pljava/src/main/java/Task2.java
+++ b/challenge-305/luca-ferrari/pljava/src/main/java/Task2.java
diff --git a/challenge-306/luca-ferrari/plperl/ch-1.plperl b/challenge-305/luca-ferrari/plperl/ch-1.plperl
index ef52151fbe..ef52151fbe 100644
--- a/challenge-306/luca-ferrari/plperl/ch-1.plperl
+++ b/challenge-305/luca-ferrari/plperl/ch-1.plperl
diff --git a/challenge-306/luca-ferrari/plperl/ch-2.plperl b/challenge-305/luca-ferrari/plperl/ch-2.plperl
index b684e6ed87..b684e6ed87 100644
--- a/challenge-306/luca-ferrari/plperl/ch-2.plperl
+++ b/challenge-305/luca-ferrari/plperl/ch-2.plperl
diff --git a/challenge-306/luca-ferrari/plpgsql/ch-1.sql b/challenge-305/luca-ferrari/plpgsql/ch-1.sql
index 1739abe155..1739abe155 100644
--- a/challenge-306/luca-ferrari/plpgsql/ch-1.sql
+++ b/challenge-305/luca-ferrari/plpgsql/ch-1.sql
diff --git a/challenge-306/luca-ferrari/plpgsql/ch-2.sql b/challenge-305/luca-ferrari/plpgsql/ch-2.sql
index c973eb42f6..c973eb42f6 100644
--- a/challenge-306/luca-ferrari/plpgsql/ch-2.sql
+++ b/challenge-305/luca-ferrari/plpgsql/ch-2.sql
diff --git a/challenge-306/luca-ferrari/python/ch-1.py b/challenge-305/luca-ferrari/python/ch-1.py
index 29b961e251..29b961e251 100644
--- a/challenge-306/luca-ferrari/python/ch-1.py
+++ b/challenge-305/luca-ferrari/python/ch-1.py
diff --git a/challenge-306/luca-ferrari/python/ch-2.py b/challenge-305/luca-ferrari/python/ch-2.py
index 5f98742484..5f98742484 100644
--- a/challenge-306/luca-ferrari/python/ch-2.py
+++ b/challenge-305/luca-ferrari/python/ch-2.py
diff --git a/challenge-306/luca-ferrari/raku/ch-1.raku b/challenge-305/luca-ferrari/raku/ch-1.raku
index 565ee6744e..565ee6744e 100644
--- a/challenge-306/luca-ferrari/raku/ch-1.raku
+++ b/challenge-305/luca-ferrari/raku/ch-1.raku
diff --git a/challenge-306/luca-ferrari/raku/ch-2.raku b/challenge-305/luca-ferrari/raku/ch-2.raku
index 5fc73464f6..5fc73464f6 100644
--- a/challenge-306/luca-ferrari/raku/ch-2.raku
+++ b/challenge-305/luca-ferrari/raku/ch-2.raku
diff --git a/challenge-305/perlboy1967/perl/ch1.pl b/challenge-305/perlboy1967/perl/ch-1.pl
index fe30952f58..fe30952f58 100755
--- a/challenge-305/perlboy1967/perl/ch1.pl
+++ b/challenge-305/perlboy1967/perl/ch-1.pl
diff --git a/challenge-305/perlboy1967/perl/ch2.pl b/challenge-305/perlboy1967/perl/ch-2.pl
index ca3e7d4e52..ca3e7d4e52 100755
--- a/challenge-305/perlboy1967/perl/ch2.pl
+++ b/challenge-305/perlboy1967/perl/ch-2.pl
diff --git a/challenge-305/richard-park/apl/AlienDictionary.aplf b/challenge-305/richard-park/apl/AlienDictionary.aplf
new file mode 100644
index 0000000000..aaff84bd23
--- /dev/null
+++ b/challenge-305/richard-park/apl/AlienDictionary.aplf
@@ -0,0 +1,7 @@
+AlienDictionary←{
+⍝ ⍵: List of strings
+⍝ ⍺: Character dictionary :: simple character vector
+⍝ ←: ⍵ sorted lexicographically according to ⍺
+     ⍵[⍺⍋↑⍵]
+ }
+
diff --git a/challenge-305/richard-park/apl/BinaryPrefix.aplf b/challenge-305/richard-park/apl/BinaryPrefix.aplf
new file mode 100644
index 0000000000..c4cb1be3fe
--- /dev/null
+++ b/challenge-305/richard-park/apl/BinaryPrefix.aplf
@@ -0,0 +1,6 @@
+ BinaryPrefix←{
+⍝ ⍵: Boolean vector
+⍝ ←: Boolean vector in which 1s mark the ends of prefixes that are
+⍝    prime numbers in decimal
+     2=+⌿0=(⍳⌈/n)∘.|n←2⊥i⌽(i←⍳≢⍵)(↑⍤0 1)⍵
+ }
diff --git a/challenge-305/richard-park/apl/W305_APL.ipynb b/challenge-305/richard-park/apl/W305_APL.ipynb
new file mode 100644
index 0000000000..aa78155342
--- /dev/null
+++ b/challenge-305/richard-park/apl/W305_APL.ipynb
@@ -0,0 +1,450 @@
+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "id": "84744954-b16a-4923-81d4-07be002b5f09",
+   "metadata": {},
+   "source": [
+    "# Perl Weekly Challenge 305\n",
+    "These are solutions to [Perl Weekly Challenge 305](https://theweeklychallenge.org/blog/perl-weekly-challenge-305/) in [Dyalog APL](https://www.dyalog.com/)."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "2829f2d3-9515-4b16-ace4-682f6aa1f044",
+   "metadata": {},
+   "source": [
+    "## Task 1: Binary Prefix\n",
+    "Take a Boolean vector as input and return a Boolean vector where a 1 indicates that the partial binary number up to that element is a prime number.\n",
+    "\n",
+    "For example, `BinaryPrefix 1 0 1` returns `0 1 1` because:\n",
+    "- $1$ is not prime\n",
+    "- $2=b_2(1 0)$ is prime\n",
+    "- $5=b_2(1 0 1)$ is prime"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "f2d288c4-392a-49db-8028-9779676bb709",
+   "metadata": {},
+   "source": [
+    "### Creating prefixes\n",
+    "There are several valid approaches. The simplest is a **catenate-scan** `,\\⍵`."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 5,
+   "id": "e23962d8-3008-4cab-9f58-ae94e726515e",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/html": [
+       "<pre class=\"language-APL\">Was ON\n",
+       "</pre>"
+      ]
+     },
+     "execution_count": 5,
+     "metadata": {},
+     "output_type": "execute_result"
+    },
+    {
+     "data": {
+      "text/html": [
+       "<pre class=\"language-APL\">┌─┬───┬─────┬───────┬─────────┬───────────┬─────────────┐\n",
+       "│1│1 0│1 0 1│1 0 1 1│1 0 1 1 0│1 0 1 1 0 1│1 0 1 1 0 1 1│\n",
+       "└─┴───┴─────┴───────┴─────────┴───────────┴─────────────┘\n",
+       "</pre>"
+      ]
+     },
+     "execution_count": 5,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "]box on\n",
+    ",\\1 0 1 1 0 1 1"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "d99ebccb-5a07-46a7-a887-bd4ef3d22a01",
+   "metadata": {},
+   "source": [
+    "We can then convert each number with the base conversion primitive."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 29,
+   "id": "6345a2a6-6168-485a-b0d6-b71bd3b35444",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/html": [
+       "<pre class=\"language-APL\">1 0 1  1  0  1  1\n",
+       "1 2 5 11 22 45 91\n",
+       "</pre>"
+      ]
+     },
+     "execution_count": 29,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "b←1 0 1 1 0 1 1\n",
+    "↑(b)(2⊥¨,\\b)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "43c244c5-7a53-4419-88ca-9cc03e1f6ace",
+   "metadata": {},
+   "source": [
+    "It can be more efficient to build a flat array that works directly with primitive functions in APL, rather than looping using the each `F¨` operator. In the following expression, we build a flat Boolean matrix of prefixes using [the rank operator](https://course.dyalog.com/cells-and-axes/#the-rank-operator). The base conversion primitive function can then work on the entire array at once rather than having to loop over individual prefixes. This is significantly faster than `2⊥¨,\\b`."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 32,
+   "id": "a10a5ebb-e7b6-437a-8927-6fd555118141",
+   "metadata": {
+    "scrolled": true
+   },
+   "outputs": [
+    {
+     "data": {
+      "text/html": [
+       "<pre class=\"language-APL\">1 2 5 11 22 45 91\n",
+       "</pre>"
+      ]
+     },
+     "execution_count": 32,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "2⊥i⌽(i←⍳≢b)(↑⍤0 1)b"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "72d3032f-7bbd-4d9f-8e89-f5e393c44d3a",
+   "metadata": {},
+   "source": [
+    "### Checking Primes\n",
+    "A direct approach is to use the \"unique divisors\" idiom."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 33,
+   "id": "43d605b8-bd1e-4589-8bfc-bae3d7e5278b",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/html": [
+       "<pre class=\"language-APL\">┌─┬───┬───┬────┬─────────┬─────────────┬─────────┐\n",
+       "│1│1 2│1 5│1 11│1 2 11 22│1 3 5 9 15 45│1 7 13 91│\n",
+       "└─┴───┴───┴────┴─────────┴─────────────┴─────────┘\n",
+       "</pre>"
+      ]
+     },
+     "execution_count": 33,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "(∪⊢∨⍳)¨1 2 5 11 22 45 91"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "b878cdaa-94e0-422c-b740-266c301634a3",
+   "metadata": {},
+   "source": [
+    "We can then count the unique divisors and check which have exactly two, which is the definition of being a prime number."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 35,
+   "id": "a035c3f8-7b4b-4dc8-bfdc-791774daa4b0",
+   "metadata": {
+    "scrolled": true
+   },
+   "outputs": [
+    {
+     "data": {
+      "text/html": [
+       "<pre class=\"language-APL\">0 1 1 1 0 0 0\n",
+       "</pre>"
+      ]
+     },
+     "execution_count": 35,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "2=(≢∘∪⊢∨⍳)¨1 2 5 11 22 45 91"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "24f817ed-67ea-4f48-aa64-f206228ba8f9",
+   "metadata": {},
+   "source": [
+    "The `(∪⊢∨⍳)` train is cute and somewhat says exactly what we want: \"unique divisors of ⍵\". However, it is quite inefficient to find all divisors between every number and the list of integers up to that number.\n",
+    "\n",
+    "Instead, let's find where all integers up to the largest in our list are evenly divided with the modulo function."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 46,
+   "id": "2e91cf5a-a8fd-4850-acfb-a5eb0f20ac7b",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/html": [
+       "<pre class=\"language-APL\">0 1 1 1 0 0 0\n",
+       "</pre>"
+      ]
+     },
+     "execution_count": 46,
+     "metadata": {}