From 3b7fa3819a985c034f0d1ad497b488a19bcdbea7 Mon Sep 17 00:00:00 2001
From: Roger Bell_West <roger@firedrake.org>
Date: Mon, 5 Jun 2023 10:31:25 +0100
Subject: RogerBW solutions for challenge no. 220

---
 challenge-220/roger-bell-west/javascript/ch-1.js |  68 +++++
 challenge-220/roger-bell-west/javascript/ch-2.js | 134 ++++++++++
 challenge-220/roger-bell-west/kotlin/ch-1.kt     |  36 +++
 challenge-220/roger-bell-west/kotlin/ch-2.kt     |  82 ++++++
 challenge-220/roger-bell-west/lua/ch-1.lua       |  76 ++++++
 challenge-220/roger-bell-west/lua/ch-2.lua       | 155 +++++++++++
 challenge-220/roger-bell-west/perl/ch-1.pl       |  27 ++
 challenge-220/roger-bell-west/perl/ch-2.pl       |  63 +++++
 challenge-220/roger-bell-west/postscript/ch-1.ps | 253 ++++++++++++++++++
 challenge-220/roger-bell-west/postscript/ch-2.ps | 323 +++++++++++++++++++++++
 challenge-220/roger-bell-west/python/ch-1.py     |  26 ++
 challenge-220/roger-bell-west/python/ch-2.py     |  51 ++++
 challenge-220/roger-bell-west/raku/ch-1.p6       |  20 ++
 challenge-220/roger-bell-west/raku/ch-2.p6       |  56 ++++
 challenge-220/roger-bell-west/ruby/ch-1.rb       |  29 ++
 challenge-220/roger-bell-west/ruby/ch-2.rb       |  45 ++++
 challenge-220/roger-bell-west/rust/ch-1.rs       |  35 +++
 challenge-220/roger-bell-west/rust/ch-2.rs       |  48 ++++
 challenge-220/roger-bell-west/tests.yaml         |  39 +++
 19 files changed, 1566 insertions(+)
 create mode 100755 challenge-220/roger-bell-west/javascript/ch-1.js
 create mode 100755 challenge-220/roger-bell-west/javascript/ch-2.js
 create mode 100644 challenge-220/roger-bell-west/kotlin/ch-1.kt
 create mode 100644 challenge-220/roger-bell-west/kotlin/ch-2.kt
 create mode 100755 challenge-220/roger-bell-west/lua/ch-1.lua
 create mode 100755 challenge-220/roger-bell-west/lua/ch-2.lua
 create mode 100755 challenge-220/roger-bell-west/perl/ch-1.pl
 create mode 100755 challenge-220/roger-bell-west/perl/ch-2.pl
 create mode 100644 challenge-220/roger-bell-west/postscript/ch-1.ps
 create mode 100644 challenge-220/roger-bell-west/postscript/ch-2.ps
 create mode 100755 challenge-220/roger-bell-west/python/ch-1.py
 create mode 100755 challenge-220/roger-bell-west/python/ch-2.py
 create mode 100755 challenge-220/roger-bell-west/raku/ch-1.p6
 create mode 100755 challenge-220/roger-bell-west/raku/ch-2.p6
 create mode 100755 challenge-220/roger-bell-west/ruby/ch-1.rb
 create mode 100755 challenge-220/roger-bell-west/ruby/ch-2.rb
 create mode 100755 challenge-220/roger-bell-west/rust/ch-1.rs
 create mode 100755 challenge-220/roger-bell-west/rust/ch-2.rs
 create mode 100644 challenge-220/roger-bell-west/tests.yaml

diff --git a/challenge-220/roger-bell-west/javascript/ch-1.js b/challenge-220/roger-bell-west/javascript/ch-1.js
new file mode 100755
index 0000000000..fa14df573c
--- /dev/null
+++ b/challenge-220/roger-bell-west/javascript/ch-1.js
@@ -0,0 +1,68 @@
+#! /usr/bin/node
+
+"use strict"
+
+// by Frank Tan
+// https://stackoverflow.com/questions/38400594/javascript-deep-comparison
+function deepEqual(a,b)
+{
+    if( (typeof a == 'object' && a != null) &&
+        (typeof b == 'object' && b != null) )
+    {
+        var count = [0,0];
+        for( var key in a) count[0]++;
+        for( var key in b) count[1]++;
+        if( count[0]-count[1] != 0) {return false;}
+        for( var key in a)
+        {
+            if(!(key in b) || !deepEqual(a[key],b[key])) {return false;}
+        }
+        for( var key in b)
+        {
+            if(!(key in a) || !deepEqual(b[key],a[key])) {return false;}
+        }
+        return true;
+    }
+    else
+    {
+        return a === b;
+    }
+}
+
+function word2set(word) {
+    let r = new Set();
+    for (let c of word.toLowerCase()) {
+        if (c >= 'a' && c <= 'z') {
+            r.add(c);
+        }
+    }
+    return r
+}
+
+function commoncharacters(lst) {
+    let c = word2set(lst[0]);
+    for (let w of lst.slice(1)) {
+        const d = word2set(w);
+        for (let l of c) {
+            if (!d.has(l)) {
+                c.delete(l);
+            }
+        }
+    }
+    let s = Array.from(c);
+    s.sort();
+    return s;
+}
+
+if (deepEqual(commoncharacters(['Perl', 'Rust', 'Raku']), ['r'])) {
+  process.stdout.write("Pass");
+} else {
+  process.stdout.write("FAIL");
+}
+process.stdout.write(" ");
+if (deepEqual(commoncharacters(['love', 'live', 'leave']), ['e', 'l', 'v'])) {
+  process.stdout.write("Pass");
+} else {
+  process.stdout.write("FAIL");
+}
+process.stdout.write("\n");
diff --git a/challenge-220/roger-bell-west/javascript/ch-2.js b/challenge-220/roger-bell-west/javascript/ch-2.js
new file mode 100755
index 0000000000..8937d6f67a
--- /dev/null
+++ b/challenge-220/roger-bell-west/javascript/ch-2.js
@@ -0,0 +1,134 @@
+#! /usr/bin/node
+
+"use strict"
+
+// by Frank Tan
+// https://stackoverflow.com/questions/38400594/javascript-deep-comparison
+function deepEqual(a,b)
+{
+    if( (typeof a == 'object' && a != null) &&
+        (typeof b == 'object' && b != null) )
+    {
+        var count = [0,0];
+        for( var key in a) count[0]++;
+        for( var key in b) count[1]++;
+        if( count[0]-count[1] != 0) {return false;}
+        for( var key in a)
+        {
+            if(!(key in b) || !deepEqual(a[key],b[key])) {return false;}
+        }
+        for( var key in b)
+        {
+            if(!(key in a) || !deepEqual(b[key],a[key])) {return false;}
+        }
+        return true;
+    }
+    else
+    {
+        return a === b;
+    }
+}
+
+function permute(a) {
+    let out = [];
+    let n=a.length;
+    let c=[];
+    for (let i = 0; i < n; i++) {
+        c.push(0);
+    }
+    out.push([...a]);
+    let i=0;
+    while (true) {
+        if (i >= n) {
+            break;
+        }
+        if (c[i] < i) {
+            if (i % 2 == 0) {
+                [a[0],a[i]] = [a[i],a[0]];
+            } else {
+                [a[c[i]],a[i]] = [a[i],a[c[i]]];
+            }
+            out.push([...a]);
+            c[i]++;
+            i=0;
+        } else {
+            c[i]=0;
+            i++;
+        }
+    }
+    return out;
+}
+
+// by VLAZ
+// https://stackoverflow.com/a/59322890
+function toWindows(inputArray, size) {
+  return Array.from(
+    {length: inputArray.length - (size - 1)}, //get the appropriate length
+    (_, index) => inputArray.slice(index, index+size) //create the windows
+  )
+}
+
+function squared(a) {
+    return a * a;
+}
+
+function decode(a0, base) {
+    let eq = [];
+    let a = a0;
+    while (a > 0) {
+        eq.unshift(a % base);
+        a = Math.trunc(a / base);
+    }
+    return eq;
+}
+
+function encode(sq, base) {
+    let a = 0;
+    for (let v of sq) {
+        a *= base;
+        a += v;
+    }
+    return a;
+}
+
+function squareful(lst) {
+    let results = new Set();
+    let squares = new Set();
+    const base = Math.max(...lst) + 1;
+    for (let la of permute(lst)) {
+        let squareful = true;
+        for (let a of toWindows(la, 2)) {
+            const cs = a[0] + a[1];
+            let mx = squared(squares.size);
+            while (cs > mx) {
+                mx = squared(squares.size + 1);
+                squares.add(mx);
+            }
+            if (!squares.has(cs)) {
+                squareful = false;
+                break;
+            }
+        }
+        if (squareful) {
+            results.add(encode(la, base));
+        }
+    }
+    let s = Array.from(results);
+    s.sort(function(a,b) {
+        return a-b;
+    });
+    return s.map(x => decode(x, base));
+}
+
+if (deepEqual(squareful([1, 17, 8]), [[1, 8, 17], [17, 8, 1]])) {
+  process.stdout.write("Pass");
+} else {
+  process.stdout.write("FAIL");
+}
+process.stdout.write(" ");
+if (deepEqual(squareful([2, 2, 2]), [[2, 2, 2]])) {
+  process.stdout.write("Pass");
+} else {
+  process.stdout.write("FAIL");
+}
+process.stdout.write("\n");
diff --git a/challenge-220/roger-bell-west/kotlin/ch-1.kt b/challenge-220/roger-bell-west/kotlin/ch-1.kt
new file mode 100644
index 0000000000..dcddd560c5
--- /dev/null
+++ b/challenge-220/roger-bell-west/kotlin/ch-1.kt
@@ -0,0 +1,36 @@
+fun word2set(word: String): MutableSet<Char> {
+    var r = mutableSetOf<Char>()
+    for (c in word.lowercase()) {
+        if (c >= 'a' && c <= 'z') {
+            r.add(c)
+        }
+    }
+    return r
+}
+
+fun commoncharacters(lst: List<String>): List<Char> {
+    var c = word2set(lst[0])
+    for (w in lst.drop(1)) {
+        c = c.intersect(word2set(w)).toMutableSet()
+    }
+    var s = ArrayList(c)
+    s.sort()
+    return s.toList()
+}
+
+fun main() {
+
+    if (commoncharacters(listOf("Perl", "Rust", "Raku")) == listOf('r')) {
+        print("Pass")
+    } else {
+        print("Fail")
+    }
+    print(" ")
+    if (commoncharacters(listOf("love", "live", "leave")) == listOf('e', 'l', 'v')) {
+        print("Pass")
+    } else {
+        print("Fail")
+    }
+    println("")
+
+}
diff --git a/challenge-220/roger-bell-west/kotlin/ch-2.kt b/challenge-220/roger-bell-west/kotlin/ch-2.kt
new file mode 100644
index 0000000000..02832eb560
--- /dev/null
+++ b/challenge-220/roger-bell-west/kotlin/ch-2.kt
@@ -0,0 +1,82 @@
+fun permute(aa: List<Int>): ArrayList<List<Int>> {
+    var a = ArrayList<Int>()
+    for (i in aa) {
+        a.add(i)
+    }
+    var out = ArrayList<List<Int>>()
+    val n = a.size
+    var c = ArrayList<Int>();
+    for (i in 0..n-1) {
+        c.add(0)
+    }
+    out.add(a.toList())
+    var i = 0
+    while (true) {
+        if (i >= n) {
+            break
+        }
+        if (c[i] < i) {
+            if (i % 2 == 0) {
+                val tmp = a[0]
+                a[0] = a[i]
+                a[i] = tmp
+            } else {
+                val tmp = a[c[i]]
+                a[c[i]] = a[i]
+                a[i] = tmp
+            }
+            out.add(a.toList())
+            c[i] += 1
+            i = 0
+        } else {
+            c[i] = 0
+            i += 1
+        }
+    }
+    return out
+}
+
+fun squared(a: Int): Int {
+    return a * a
+}
+
+fun squareful(lst: List<Int>): List<List<Int>> {
+    var results = mutableSetOf<List<Int>>()
+    var squares = mutableSetOf<Int>()
+    for (la in permute(lst)) {
+        var squareful = true
+        for (a in la.windowed(size = 2)) {
+            val cs = a[0] + a[1]
+            var mx = squared(squares.size)
+            while (cs > mx) {
+                mx = squared(squares.size + 1)
+                squares.add(mx)
+            }
+            if (!squares.contains(cs)) {
+                squareful = false
+                break
+            }
+        }
+        if (squareful) {
+            results.add(la)
+        }
+    }
+    return results.toList()
+}
+
+fun main() {
+
+    if (squareful(listOf(1, 17, 8)) == listOf(listOf(1, 8, 17), listOf(17, 8, 1))) {
+        print("Pass")
+    } else {
+        print("Fail")
+    }
+    print(" ")
+    if (squareful(listOf(2, 2, 2)) == listOf(listOf(2, 2, 2))) {
+        print("Pass")
+    } else {
+        print("Fail")
+    }
+    println("")
+
+}
diff --git a/challenge-220/roger-bell-west/lua/ch-1.lua b/challenge-220/roger-bell-west/lua/ch-1.lua
new file mode 100755
index 0000000000..74624b0e7e
--- /dev/null
+++ b/challenge-220/roger-bell-west/lua/ch-1.lua
@@ -0,0 +1,76 @@
+#! /usr/bin/lua
+
+-- by Michael Anderson at
+-- https://stackoverflow.com/questions/8722620/comparing-two-index-tables-by-index-value-in-lua
+-- modified by Roger
+function recursive_compare(t1,t2)
+  -- Use usual comparison first.
+  if t1==t2 then return true end
+  -- We only support non-default behavior for tables
+  if (type(t1)~="table") then return false end
+  -- They better have the same metatables
+  local mt1 = getmetatable(t1)
+  local mt2 = getmetatable(t2)
+  if( not recursive_compare(mt1,mt2) ) then return false end
+  -- Build list of all keys
+  local kk = {}
+  for k1, _ in pairs(t1) do
+     kk[k1] = true
+  end
+  for k2, _ in pairs(t2) do
+     kk[k2] = true
+  end
+  -- Check each key that exists in at least one table
+  for _, k in ipairs(kk) do
+     if (not recursive_compare(t1[k], t2[k])) then
+        return false
+     end
+  end
+  return true
+end
+
+function keys(t)
+   local a = {}
+   for k, v in pairs(t) do
+      table.insert(a, k)
+   end
+   return a
+end
+
+function word2set(word)
+   local s = {}
+   for c in string.gmatch(string.lower(word), "%a") do
+      s[c] = true
+   end
+   return s
+end
+
+function commoncharacters(lst)
+   local c = word2set(lst[1])
+   for i = 2, #lst do
+      local d = word2set(lst[i])
+      for k, _ in pairs(c) do
+         if d[k] == nil then
+            c[k] = nil
+         end
+      end
+   end
+   local o = keys(c)
+   table.sort(o)
+   return o
+end
+
+if recursive_compare(commoncharacters({"Perl", "Rust", "Raku"}), {"r"}) then
+  io.write("Pass")
+else
+  io.write("FAIL")
+end
+io.write(" ")
+
+if recursive_compare(commoncharacters({"love", "live", "leave"}), {"e", "l", "v"}) then
+  io.write("Pass")
+else
+  io.write("FAIL")
+end
+print("")
+
diff --git a/challenge-220/roger-bell-west/lua/ch-2.lua b/challenge-220/roger-bell-west/lua/ch-2.lua
new file mode 100755
index 0000000000..57254c3a40
--- /dev/null
+++ b/challenge-220/roger-bell-west/lua/ch-2.lua
@@ -0,0 +1,155 @@
+#! /usr/bin/lua
+
+-- by Michael Anderson at
+-- https://stackoverflow.com/questions/8722620/comparing-two-index-tables-by-index-value-in-lua
+-- modified by Roger
+function recursive_compare(t1,t2)
+  -- Use usual comparison first.
+  if t1==t2 then return true end
+  -- We only support non-default behavior for tables
+  if (type(t1)~="table") then return false end
+  -- They better have the same metatables
+  local mt1 = getmetatable(t1)
+  local mt2 = getmetatable(t2)
+  if( not recursive_compare(mt1,mt2) ) then return false end
+  -- Build list of all keys
+  local kk = {}
+  for k1, _ in pairs(t1) do
+     kk[k1] = true
+  end
+  for k2, _ in pairs(t2) do
+     kk[k2] = true
+  end
+  -- Check each key that exists in at least one table
+  for k, _ in pairs(kk) do
+     if (not recursive_compare(t1[k], t2[k])) then
+        return false
+     end
+  end
+  return true
+end
+
+function keys(t)
+   local a = {}
+   for k, v in pairs(t) do
+      table.insert(a, k)
+   end
+   return a
+end
+
+function deepcopy(src)
+   local dst = {}
+   for k, v in pairs(src) do
+      if type(v) == "table" then
+         v = deepcopy(v)
+      end
+      dst[k] = v
+   end
+   return dst
+end
+
+function permute(a)
+   local out = {}
+   local n = #a
+   local c = {}
+   for i = 1,n do
+      table.insert(c, 1)
+   end
+   table.insert(out, deepcopy(a))
+   local i=1
+   while true do
+      if i > n then
+         break
+      end
+      if c[i] < i then
+         if i % 2 == 1 then
+            a[1],a[i] = a[i],a[1]
+         else
+            a[c[i]],a[i] = a[i],a[c[i]]
+         end
+         table.insert(out, deepcopy(a))
+         c[i] = c[i]+1
+         i = 1
+      else
+         c[i] = 1
+         i = i+1
+      end
+   end
+   return out
+end
+
+function propersize(t)
+   local l=0
+   for k,v in pairs(t) do
+      l = l + 1
+   end
+   return l
+end
+
+function squared(a)
+   return a * a
+end
+
+function encode(sq, base)
+   local a = 0
+   for _, v in ipairs(sq) do
+      a = a * base
+      a = a + v
+   end
+   return a
+end
+
+function decode(a, base)
+   local eq = {}
+   while a > 0 do
+      table.insert(eq, 1, a % base)
+      a = a // base
+   end
+   return eq
+end
+
+function squareful(lst)
+   local results = {}
+   local squares = {}
+   local base = math.max(table.unpack(lst)) + 1
+   for _, la in ipairs(permute(lst)) do
+      local squareful = true
+      for i = 1, #la-1 do
+         local cs = la[i] + la[i + 1]
+         local mx = squared(propersize(squares))
+         while cs > mx do
+            mx = squared(propersize(squares) + 1)
+            squares[mx] = true
+         end
+         if squares[cs] == nil then
+            squareful = false
+            break
+         end
+      end
+      if squareful then
+         results[encode(la, base)] = true
+      end
+   end
+   local o = keys(results)
+   table.sort(o)
+   local out = {}
+   for _, v in ipairs(o) do
+      table.insert(out, decode(v, base))
+   end
+   return out
+end
+
+if recursive_compare(squareful({1, 17, 8}), {{1, 8, 17}, {17, 8, 1}}) then
+  io.write("Pass")
+else
+  io.write("FAIL")
+end
+io.write(" ")
+
+if recursive_compare(squareful({2, 2, 2}), {{2, 2, 2}}) then
+  io.write("Pass")
+else
+  io.write("FAIL")
+end
+print("")
+
diff --git a/challenge-220/roger-bell-west/perl/ch-1.pl b/challenge-220/roger-bell-west/perl/ch-1.pl
new file mode 100755
index 0000000000..9370a80063
--- /dev/null
+++ b/challenge-220/roger-bell-west/perl/ch-1.pl
@@ -0,0 +1,27 @@
+#! /usr/bin/perl
+
+use strict;
+use warnings;
+use experimental 'signatures';
+
+use Test::More tests => 2;
+
+is_deeply(commoncharacters(['Perl', 'Rust', 'Raku']), ['r'], 'example 1');
+is_deeply(commoncharacters(['love', 'live', 'leave']), ['e', 'l', 'v'], 'example 2');
+
+sub word2set($word) {
+  return {map {$_ => 1} grep /[a-z]/, split '', lc($word)};
+}
+
+sub commoncharacters($lst) {
+  my $c = word2set($lst->[0]);
+  foreach my $si (1 .. $#{$lst}) {
+    my $d = word2set($lst->[$si]);
+    foreach my $l (keys %{$c}) {
+      unless (exists $d->{$l}) {
+        delete $c->{$l};
+      }
+    }
+  }
+  return [sort keys %{$c}];
+}
diff --git a/challenge-220/roger-bell-west/perl/ch-2.pl b/challenge-220/roger-bell-west/perl/ch-2.pl
new file mode 100755
index 0000000000..4785f189c4
--- /dev/null
+++ b/challenge-220/roger-bell-west/perl/ch-2.pl
@@ -0,0 +1,63 @@
+#! /usr/bin/perl
+
+use strict;
+use warnings;
+use experimental 'signatures';
+
+use Algorithm::Permute;
+use List::Util qw(max);
+
+use Test::More tests => 2;
+
+is_deeply(squareful([1, 17, 8]), [[1, 8, 17], [17, 8, 1]], 'example 1');
+is_deeply(squareful([2, 2, 2]), [[2, 2, 2]], 'example 2');
+
+
+sub squared($a) {
+  return $a * $a;
+}
+
+sub decode($a0, $base) {
+  my @eq;
+  my $a = $a0;
+  while ($a > 0) {
+    unshift @eq, $a % $base;
+    $a = int($a / $base);
+  }
+  return \@eq;
+}
+
+sub encode($sq, $base) {
+  my $a = 0;
+  foreach my $v (@{$sq}) {
+    $a *= $base;
+    $a += $v;
+  }
+  return $a;
+}
+
+sub squareful($lst) {
+  my %results;
+  my %squares;
+  my $base = max(@{$lst}) + 1;
+  my $p = Algorithm::Permute->new($lst);
+  while (my @la = $p->next) {
+    my $squareful = 1;
+    foreach my $i (0 .. $#la - 1) {
+      my $cs = $la[$i] + $la[$i + 1];
+      my $mx = squared(scalar keys %squares);
+      while ($cs > $mx) {
+        $mx = squared((scalar keys %squares) + 1);
+        $squares{$mx} = 1;
+      }
+      unless (exists $squares{$cs}) {
+        $squareful = 0;
+        last;
+      }
+    }
+    if ($squareful) {
+      $results{encode(\@la, $base)} = 1;
+    }
+  }
+  return [map {decode($_, $base)} sort {$a <=> $b} keys %results];
+}
diff --git a/challenge-220/roger-bell-west/postscript/ch-1.ps b/challenge-220/roger-bell-west/postscript/ch-1.ps
new file mode 100644
index 0000000000..d46e25cd53
--- /dev/null
+++ b/challenge-220/roger-bell-west/postscript/ch-1.ps
@@ -0,0 +1,253 @@
+%!PS
+
+% begin included library code
+% see https://codeberg.org/Firedrake/postscript-libraries/
+/map { % array proc -> array
+    2 dict begin
+    /p exch def
+    [ exch
+      {
+          p
+      } forall
+    ]
+    end
+} bind def
+
+/s2a {
+    [ exch { } forall ]
+} bind def
+
+/quicksort.main { % lo hi -> (null)
+    3 dict begin
+    /hi exch def
+    /lo exch def
+    /xit false def
+    lo 0 lt {
+        /xit true def
+    } if
+    hi 0 lt {
+        /xit true def
+    } if
+    lo hi ge {
+        /xit true def
+    } if
+    xit not {
+        /p quicksort.partition def
+        lo p quicksort.main
+        p 1 add hi quicksort.main
+    } if
+    end
+} bind def
+
+/quicksort.with_comparator { % [ a c b ] { comparator } -> [ a b c ]
+    2 dict begin
+    /cmp exch def
+    /arr exch def
+    arr length 0 gt {
+        0 arr length 1 sub quicksort.main
+    } if
+    arr
+    end
+} bind def
+
+/quicksort.swap {
+    2 dict begin
+    /bi exch def
+    /ai exch def
+    arr ai get
+    arr bi get
+    arr exch ai exch put
+    arr exch bi exch put
+    end
+} bind def
+
+/quicksort.partition {
+    3 dict begin
+    /pivot arr hi lo add 2 idiv get def
+    /i lo 1 sub def
+    /j hi 1 add def
+    {
+        {
+            /i i 1 add def
+            arr i get pivot cmp 0 ge {
+                exit
+            } if
+        } loop
+        {
+            /j j 1 sub def
+            arr j get pivot cmp 0 le {
+                exit
+            } if
+        } loop
+        i j ge {
+            j
+            exit
+        } if
+        i j quicksort.swap
+    } loop
+    end
+} bind def
+
+/deepeq {
+    2 dict begin
+    /a exch def
+    /b exch def
+    a type b type eq {
+        a type /dicttype eq {
+            a length b length eq {
+                <<
+                    a {
+                        pop
+                        true
+                    } forall
+                    b {
+                        pop
+                        true
+                    } forall
+                >>
+                true exch
+                {
+                    pop
+                    dup a exch known {
+                        dup b exch known {
+                            dup a exch get exch b exch get deepeq not {
+                                pop false
+                            } if
+                        } {
+                            false
+                        } ifelse
+                    } {
+                        false
+                    } ifelse
+                } forall
+            } {
+                false
+            } ifelse
+        } {
+            a type dup /arraytype eq exch /stringtype eq or {
+                a length b length eq {
+                    true
+                    0 1 a length 1 sub {
+                        dup a exch get exch b exch get deepeq not {
+                            pop false
+                            exit
+                        } if
+                    } for
+                } {
+                    false
+                } ifelse
+            } {
+                a b eq
+            } ifelse
+        } ifelse
+    } {
+        false
+    } ifelse
+    end
+} bind def
+
+/toset { % array -> dict of (value, true)
+    << exch
+       {
+           true
+       } forall
+    >>
+} bind def
+
+/quicksort.cmp {
+    2 copy
+    lt {
+        pop pop -1
+    } {
+        gt {
+            1
+        } {
+            0
+        } ifelse
+    } ifelse
+} bind def
+
+/test.start {
+    print (:) print
+    /test.pass 0 def
+    /test.count 0 def
+} bind def
+
+/test.end {
+    ( ) print
+    test.count 0 gt {
+        (Passed ) print
+        test.pass (...) cvs print
+        (/) print
+        test.count (...) cvs print
+        ( \() print
+        test.pass 100 mul test.count idiv (...) cvs print
+        (%\)) print
+        (\r\n) print
+    } if
+} bind def
+
+/quicksort {
+    { quicksort.cmp } quicksort.with_comparator
+} bind def
+
+/keys { % dict -> array of dict keys
+    [ exch
+      {
+          pop
+      } forall
+    ]
+} bind def
+
+/test {
+    /test.count test.count 1 add def
+    {
+        /test.pass test.pass 1 add def
+    } {
+        ( ) print
+        test.count (....) cvs print
+        (-fail) print
+    } ifelse
+} bind def
+
+
+% end included library code
+
+/word2set {
+    1 dict begin
+    [ exch
+      s2a {
+          /ch exch def
+          ch 65 ge ch 90 le and {
+              ch 32 add
+          } {
+              ch 97 ge ch 122 le and {
+                  ch
+              } if
+          } ifelse
+      } forall
+    ] toset
+    end
+} bind def
+
+/commoncharacters {
+    4 dict begin
+    /lst exch def
+    /c lst 0 get word2set def
+    1 1 lst length 1 sub {
+        lst exch get word2set /d exch def
+        c keys {
+            /k exch def
+            d k known not {
+                c k undef
+            } if
+        } forall
+    } for
+    c keys quicksort { 1 string dup 0 4 -1 roll put } map
+    end
+} bind def
+
+(commoncharacters) test.start
+[(Perl) (Rust) (Raku)] commoncharacters [(r)] deepeq test
+[(love) (live) (leave)] commoncharacters [(e) (l) (v)] deepeq test
+test.end
diff --git a/challenge-220/roger-bell-west/postscript/ch-2.ps b/challenge-220/roger-bell-west/postscript/ch-2.ps
new file mode 100644
index 0000000000..b47b145c36
--- /dev/null
+++ b/challenge-220/roger-bell-west/postscript/ch-2.ps
@@ -0,0 +1,323 @@
+%!PS
+
+% begin included library code
+% see https://codeberg.org/Firedrake/postscript-libraries/
+/test.end {
+    ( ) print
+    test.count 0 gt {
+        (Passed ) print
+        test.pass (...) cvs print
+        (/) print
+        test.count (...) cvs print
+        ( \() print
+        test.pass 100 mul test.count idiv (...) cvs print
+        (%\)) print
+        (\r\n) print
+    } if
+} bind def
+
+/reverse {
+    1 dict begin
+    dup length /l exch def
+    [ exch
+      aload pop
+      2 1 l {
+          -1 roll
+      } for
+    ]
+    end
+} bind def
+
+/listmax {
+    { max } reduce
+} bind def
+
+/keys { % dict -> array of dict keys
+    [ exch
+      {
+          pop
+      } forall
+    ]
+} bind def
+
+/quicksort.with_comparator { % [ a c b ] { comparator } -> [ a b c ]
+    2 dict begin
+    /cmp exch def
+    /arr exch def
+    arr length 0 gt {
+        0 arr length 1 sub quicksort.main
+    } if
+    arr
+    end
+} bind def
+
+/permute { % [array] {proc} permute runs proc on each permutation of array
+    7 dict begin
+    /permute.subproc exch def
+    /permute.a exch def
+    /permute.n permute.a length def
+    /permute.c [ permute.n { 0 } repeat ] def
+    permute.a permute.subproc
+    /permute.i 0 def
+    {
+        permute.i permute.n ge {
+            exit
+        } if
+        permute.c permute.i get permute.i lt {
+            permute.i 2 mod 0 eq {
+                0 permute.i permute.swap
+            } {
+                permute.c permute.i get permute.i permute.swap
+            } ifelse
+            permute.a permute.subproc
+            permute.c permute.i get 1 add permute.c exch permute.i exch put
+            /permute.i 0 def
+        } {
+            permute.c permute.i 0 put
+            /permute.i permute.i 1 add def
+        } ifelse
+    } loop
+    end
+} bind def
+
+/permute.swap {
+    /permute.bi exch def
+    /permute.ai exch def
+    permute.a permute.ai get
+    permute.a permute.bi get
+    permute.a exch permute.ai exch put
+    permute.a exch permute.bi exch put
+} bind def
+
+/quicksort.cmp {
+    2 copy
+    lt {
+        pop pop -1
+    } {
+        gt {
+            1
+        } {
+            0
+        } ifelse
+    } ifelse
+} bind def
+
+/quicksort {
+    { quicksort.cmp } quicksort.with_comparator
+} bind def
+
+/quicksort.swap {
+    2 dict begin
+    /bi exch def
+    /ai exch def
+    arr ai get
+    arr bi get
+    arr exch ai exch put
+    arr exch bi exch put
+    end
+} bind def
+
+/toset { % array -> dict of (value, true)
+    << exch
+       {
+           true
+       } forall
+    >>
+} bind def
+
+/quicksort.partition {
+    3 dict begin
+    /pivot arr hi lo add 2 idiv get def
+    /i lo 1 sub def
+    /j hi 1 add def
+    {
+        {
+            /i i 1 add def
+            arr i get pivot cmp 0 ge {
+                exit
+            } if
+        } loop
+        {
+            /j j 1 sub def
+            arr j get pivot cmp 0 le {
+                exit
+            } if
+        } loop
+        i j ge {
+            j
+            exit
+        } if
+        i j quicksort.swap
+    } loop
+    end
+} bind def
+
+/reduce { % array proc -> value
+    2 dict begin
+    /p exch def
+    /a exch def
+    a 0 get
+    1 1 a length 1 sub {
+        a exch get
+        p
+    } for
+    end
+} bind def
+
+/test.start {
+    print (:) print
+    /test.pass 0 def
+    /test.count 0 def
+} bind def
+
+/test {
+    /test.count test.count 1 add def
+    {
+        /test.pass test.pass 1 add def
+    } {
+        ( ) print
+        test.count (....) cvs print
+        (-fail) print
+    } ifelse
+} bind def
+
+/deepeq {
+    2 dict begin
+    /a exch def
+    /b exch def
+    a type b type eq {
+        a type /dicttype eq {
+            a length b length eq {
+                <<
+                    a {
+                        pop
+                        true
+                    } forall
+                    b {
+                        pop
+                        true
+                    } forall
+                >>
+                true exch
+                {
+                    pop
+                    dup a exch known {
+                        dup b exch known {
+                            dup a exch get exch b exch get deepeq not {
+                                pop false
+                            } if
+                        } {
+                            false
+                        } ifelse
+                    } {
+                        false
+                    } ifelse
+                } forall
+            } {
+                false
+            } ifelse
+        } {
+            a type dup /arraytype eq exch /stringtype eq or {
+                a length b length eq {
+                    true
+                    0 1 a length 1 sub {
+                        dup a exch get exch b exch get deepeq not {
+                            pop false
+                            exit
+                        } if
+                    } for
+                } {
+                    false
+                } ifelse
+            } {
+                a b eq
+            } ifelse
+        } ifelse
+    } {
+        false
+    } ifelse
+    end
+} bind def
+
+/quicksort.main { % lo hi -> (null)
+    3 dict begin
+    /hi exch def
+    /lo exch def
+    /xit false def
+    lo 0 lt {
+        /xit true def
+    } if
+    hi 0 lt {
+        /xit true def
+    } if
+    lo hi ge {
+        /xit true def
+    } if
+    xit not {
+        /p quicksort.partition def
+        lo p quicksort.main
+        p 1 add hi quicksort.main
+    } if
+    end
+} bind def
+
+
+% end included library code
+
+/squareful {
+    0 dict begin
+    /lst exch def
+    /squares 0 dict def
+    /results [
+        lst {
+            /la exch def
+            /squareful true def
+            0 1 la length 2 sub {
+                dup
+                1 add la exch get
+                exch
+                la exch get
+                add
+                /cs exch def
+                /mx squares length dup mul def
+                {
+                    cs mx le {
+                        exit
+                    } if
+                    /mx squares length 1 add dup mul def
+                    squares mx true put
+                } loop
+                squares cs known not {
+                    /squareful false def
+                    exit
+                } if
+            } for
+            squareful {
+                [ la aload pop ]
+            } if
+        } permute
+    ] def
+    /base lst listmax 1 add def
+    [
+        [
+            results {
+                { exch base mul add } reduce
+            } forall
+        ] toset keys quicksort {
+            [ exch
+              {
+                  dup 0 eq {
+                      pop exit
+                  } if
+                  dup base mod exch base idiv
+              } loop
+            ] reverse
+        } forall
+    ]
+    end
+} bind def
+
+(squareful) test.start
+[1 17 8] squareful [[1 8 17] [17 8 1]] deepeq test
+[2 2 2] squareful [[2 2 2]] deepeq test
+test.end
diff --git a/challenge-220/roger-bell-west/python/ch-1.py b/challenge-220/roger-bell-west/python/ch-1.py
new file mode 100755
index 0000000000..a9f0d23e3b
--- /dev/null
+++ b/challenge-220/roger-bell-west/python/ch-1.py
@@ -0,0 +1,26 @@
+#! /usr/bin/python3
+
+def word2set(word):
+  r = set()
+  for c in word.lower():
+    if c >= 'a' and c <= 'z':
+      r.add(c)
+  return r
+
+def commoncharacters(lst):
+  c = word2set(lst[0])
+  for w in lst[1:]:
+    c = c.intersection(word2set(w))
+  return sorted(list(c))
+
+import unittest
+
+class TestCommoncharacters(unittest.TestCase):
+
+  def test_ex1(self):
+    self.assertEqual(commoncharacters(["Perl", "Rust", "Raku"]), ["r"], 'example 1')
+
+  def test_ex2(self):
+    self.assertEqual(commoncharacters(["love", "live", "leave"]), ["e", "l", "v"], 'example 2')
+
+unittest.main()
diff --git a/challenge-220/roger-bell-west/python/ch-2.py b/challenge-220/roger-bell-west/python/ch-2.py
new file mode 100755
index 0000000000..b9fc7f9c51
--- /dev/null
+++ b/challenge-220/roger-bell-west/python/ch-2.py
@@ -0,0 +1,51 @@
+#! /usr/bin/python3
+
+import collections
+from itertools import permutations, islice
+
+# https://docs.python.org/3/library/itertools.html
+def sliding_window(iterable, n):
+    # sliding_window('ABCDEFG', 4) --> ABCD BCDE CDEF DEFG
+    it = iter(iterable)
+    window = collections.deque(islice(it, n), maxlen=n)
+    if len(window) == n:
+        yield tuple(window)
+    for x in it:
+        window.append(x)
+        yield tuple(window)
+
+def squared(a):
+  return a * a
+
+def squareful(lst):
+  results = set()
+  squares = set()
+  for la in permutations(lst):
+    squareful = True
+    for a in sliding_window(la, 2):
+      cs = a[0] + a[1]
+      mx = squared(len(squares))
+      while cs > mx:
+        mx = squared(len(squares) + 1)
+        squares.add(mx)
+      if cs not in squares:
+        squareful = False
+        break
+    if squareful:
+      results.add(tuple(la))
+  o = list(results)
+  o.sort()
+  return [ list(x) for x in o ]
+
+
+import unittest
+
+class TestSquareful(unittest.TestCase):
+
+  def test_ex1(self):
+    self.assertEqual(squareful([1, 17, 8]), [[1, 8, 17], [17, 8, 1]], 'example 1')
+
+  def test_ex2(self):
+    self.assertEqual(squareful([2, 2, 2]), [[2, 2, 2]], 'example 2')
+
+unittest.main()
diff --git a/challenge-220/roger-bell-west/raku/ch-1.p6 b/challenge-220/roger-bell-west/raku/ch-1.p6
new file mode 100755
index 0000000000..cc9f09f8a6
--- /dev/null
+++ b/challenge-220/roger-bell-west/raku/ch-1.p6
@@ -0,0 +1,20 @@
+#! /usr/bin/raku
+
+use Test;
+
+plan 2;
+
+is-deeply(commoncharacters(['Perl', 'Rust', 'Raku']), ['r'], 'example 1');
+is-deeply(commoncharacters(['love', 'live', 'leave']), ['e', 'l', 'v'], 'example 2');
+
+sub word2set($word) {
+  return SetHash($word.lc.comb.grep(/<[a..z]>/));
+}
+
+sub commoncharacters(@lst) {
+    my $c = word2set(@lst[0]);
+    for @lst.skip(1) -> $w {
+        $c (&)= word2set($w);
+    }
+    return $c.keys.sort.Array;
+}
diff --git a/challenge-220/roger-bell-west/raku/ch-2.p6 b/challenge-220/roger-bell-west/raku/ch-2.p6
new file mode 100755
index 0000000000..aae0b4e697
--- /dev/null
+++ b/challenge-220/roger-bell-west/raku/ch-2.p6
@@ -0,0 +1,56 @@
+#! /usr/bin/raku
+
+use Test;
+
+plan 2;
+
+is-deeply(squareful([1, 17, 8]), [[1, 8, 17], [17, 8, 1]], 'example 1');
+is-deeply(squareful([2, 2, 2]), [[2, 2, 2],], 'example 2');
+
+sub squared($a) {
+    return $a * $a;
+}
+
+sub decode($a0, $base) {
+    my @eq;
+    my $a = $a0;
+    while ($a > 0) {
+        @eq.unshift($a % $base);
+        $a div= $base;
+    }
+    return @eq;
+}
+
+sub encode(@sq, $base) {
+    my $a = 0;
+    for @sq -> $v {
+        $a *= $base;
+        $a += $v;
+    }
+    return $a;
+}
+
+sub squareful(@lst) {
+    my $results = SetHash.new;
+    my $squares = SetHash.new;
+    my $base = max(@lst) + 1;
+    for @lst.permutations -> @la {
+        my $squareful = True;
+        for @la.rotor(2 => -1) -> @a {
+            my $cs = @a[0] + @a[1];
+            my $mx = squared($squares.elems);
+            while ($cs > $mx) {
+                $mx = squared($squares.elems + 1);
+                $squares{$mx}++;
+            }
+            unless ($squares{$cs}:exists) {
+                $squareful = False;
+                last;
+            }
+        }
+        if ($squareful) {
+            $results{encode(@la, $base)}++;
+        }
+    }
+    return $results.keys.sort({$^a <=> $^b}).map({decode($_, $base)}).Array;
+}
diff --git a/challenge-220/roger-bell-west/ruby/ch-1.rb b/challenge-220/roger-bell-west/ruby/ch-1.rb
new file mode 100755
index 0000000000..54ae5ca678
--- /dev/null
+++ b/challenge-220/roger-bell-west/ruby/ch-1.rb
@@ -0,0 +1,29 @@
+#! /usr/bin/ruby
+
+require 'set'
+
+def word2set(word)
+  return Set.new(word.downcase.chars.find_all {|i| i >= 'a' && i <= 'z'})
+end
+
+def commoncharacters(lst)
+  c = word2set(lst[0])
+  lst.drop(1).each do |w|
+    c = c & word2set(w)
+  end
+  return c.to_a.sort
+end
+
+require 'test/unit'
+
+class TestCommoncharacters < Test::Unit::TestCase
+
+  def test_ex1
+    assert_equal(['r'], commoncharacters(['Perl', 'Rust', 'Raku']))
+  end
+
+  def test_ex2
+    assert_equal(['e', 'l', 'v'], commoncharacters(['love', 'live', 'leave']))
+  end
+
+end
diff --git a/challenge-220/roger-bell-west/ruby/ch-2.rb b/challenge-220/roger-bell-west/ruby/ch-2.rb
new file mode 100755
index 0000000000..65679c8e9d
--- /dev/null
+++ b/challenge-220/roger-bell-west/ruby/ch-2.rb
@@ -0,0 +1,45 @@
+#! /usr/bin/ruby
+
+require 'set'
+
+def squared(a)
+  return a * a
+end
+
+def squareful(lst)
+  results = Set.new
+  squares = Set.new
+  lst.permutation do |la|
+    squareful = true
+    la.each_cons(2) do |a|
+      cs = a[0] + a[1]
+      mx = squared(squares.length)
+      while cs > mx do
+        mx = squared(squares.length + 1)
+        squares.add(mx)
+      end
+      if !squares.include?(cs) then
+        squareful = false
+        break
+      end
+    end
+    if squareful then
+      results.add(la)
+    end
+  end
+  return results.to_a.sort
+end
+
+require 'test/unit'
+
+class TestSquareful < Test::Unit::TestCase
+
+  def test_ex1
+    assert_equal([[1, 8, 17], [17, 8, 1]], squareful([1, 17, 8]))
+  end
+
+  def test_ex2
+    assert_equal([[2, 2, 2]], squareful([2, 2, 2]))
+  end
+
+end
diff --git a/challenge-220/roger-bell-west/rust/ch-1.rs b/challenge-220/roger-bell-west/rust/ch-1.rs
new file mode 100755
index 0000000000..eee4197e66
--- /dev/null
+++ b/challenge-220/roger-bell-west/rust/ch-1.rs
@@ -0,0 +1,35 @@
+#! /bin/sh
+//usr/bin/env rustc --test $0 -o ${0}x && ./${0}x --nocapture; rm -f ${0}x ; exit
+
+use std::collections::HashSet;
+
+#[test]
+fn test_ex1() {
+    assert_eq!(commoncharacters(vec!["Perl", "Rust", "Raku"]), vec!['r']);
+}
+
+#[test]
+fn test_ex2() {
+    assert_eq!(
+        commoncharacters(vec!["love", "live", "leave"]),
+        vec!['e', 'l', 'v']
+    );
+}
+
+fn word2set(word: &str) -> HashSet<char> {
+    let mut s: HashSet<char> = HashSet::new();
+    for c in word.to_ascii_lowercase().chars() {
+        s.insert(c);
+    }
+    s
+}
+
+fn commoncharacters(lst: Vec<&str>) -> Vec<char> {
+    let mut c = word2set(lst[0]);
+    for w in lst.iter().skip(1) {
+        c = c.intersection(&word2set(w)).cloned().collect::<HashSet<char>>();
+    }
+    let mut s = c.into_iter().collect::<Vec<_>>();
+    s.sort();
+    s
+}
diff --git a/challenge-220/roger-bell-west/rust/ch-2.rs b/challenge-220/roger-bell-west/rust/ch-2.rs
new file mode 100755
index 0000000000..3d8284d43b
--- /dev/null
+++ b/challenge-220/roger-bell-west/rust/ch-2.rs
@@ -0,0 +1,48 @@
+// [dependencies]
+// itertools = "0.10.5"
+
+use itertools::Itertools;
+use std::collections::HashSet;
+
+#[test]
+fn test_ex1() {
+    assert_eq!(squareful(vec![1, 17, 8]), vec![vec![1, 8, 17], vec![17, 8, 1]]);
+}
+
+#[test]
+fn test_ex2() {
+    assert_eq!(squareful(vec![2, 2, 2]), vec![vec![2, 2, 2]]);
+}
+
+fn squared(a: u32) -> u32 {
+    a * a
+}
+
+fn squareful(lst: Vec<u32>) -> Vec<Vec<u32>> {
+    let mut results: HashSet<Vec<u32>> = HashSet::new();
+    let mut squares: HashSet<u32> = HashSet::new();
+    for la in lst.iter().permutations(lst.len()) {
+        let mut squareful = true;
+        for a in la.windows(2) {
+            let cs = a[0] + a[1];
+            let mut mx = squared(squares.len() as u32);
+            while cs > mx {
+                mx = squared(squares.len() as u32 + 1);
+                squares.insert(mx);
+            }
+            if !squares.contains(&cs) {
+                squareful = false;
+                break;
+            }
+        }
+        if squareful {
+            results.insert(la.into_iter().map(|i| *i).collect::<Vec<u32>>());
+        }
+    }
+    let mut out = Vec::new();
+    for a in results {
+        out.push(a);
+    }
+    out.sort();
+    out
+}
diff --git a/challenge-220/roger-bell-west/tests.yaml b/challenge-220/roger-bell-west/tests.yaml
new file mode 100644
index 0000000000..da885eadaf
--- /dev/null
+++ b/challenge-220/roger-bell-west/tests.yaml
@@ -0,0 +1,39 @@
+---
+ch-1:
+  - function: commoncharacters
+    arguments:
+      - Perl
+      - Rust
+      - Raku
+    result:
+      - r
+  - arguments:
+      - love
+      - live
+      - leave
+    result:
+      - e
+      - l
+      - v
+ch-2:
+  - function: squareful
+    arguments:
+      - 1
+      - 17
+      - 8
+    result:
+      - - 1
+        - 8
+        - 17
+      - - 17
+        - 8
+        - 1
+  - arguments:
+      - 2
+      - 2
+      - 2
+    result:
+      - - 2
+        - 2
+        - 2
+ 
-- 
cgit