From f406bb878bbbfa00276a10275537fac95d575cb2 Mon Sep 17 00:00:00 2001
From: Roger Bell_West <roger@firedrake.org>
Date: Tue, 13 Feb 2024 11:37:42 +0000
Subject: RogerBW solutions for challenge no. 256

---
 challenge-256/roger-bell-west/javascript/ch-1.js | 36 ++++++++++
 challenge-256/roger-bell-west/javascript/ch-2.js | 35 ++++++++++
 challenge-256/roger-bell-west/kotlin/ch-1.kt     | 36 ++++++++++
 challenge-256/roger-bell-west/kotlin/ch-2.kt     | 37 ++++++++++
 challenge-256/roger-bell-west/lua/ch-1.lua       | 37 ++++++++++
 challenge-256/roger-bell-west/lua/ch-2.lua       | 36 ++++++++++
 challenge-256/roger-bell-west/perl/ch-1.pl       | 25 +++++++
 challenge-256/roger-bell-west/perl/ch-2.pl       | 28 ++++++++
 challenge-256/roger-bell-west/postscript/ch-1.ps | 87 ++++++++++++++++++++++++
 challenge-256/roger-bell-west/postscript/ch-2.ps | 72 ++++++++++++++++++++
 challenge-256/roger-bell-west/python/ch-1.py     | 27 ++++++++
 challenge-256/roger-bell-west/python/ch-2.py     | 25 +++++++
 challenge-256/roger-bell-west/raku/ch-1.p6       | 23 +++++++
 challenge-256/roger-bell-west/raku/ch-2.p6       | 24 +++++++
 challenge-256/roger-bell-west/ruby/ch-1.rb       | 35 ++++++++++
 challenge-256/roger-bell-west/ruby/ch-2.rb       | 34 +++++++++
 challenge-256/roger-bell-west/rust/ch-1.rs       | 33 +++++++++
 challenge-256/roger-bell-west/rust/ch-2.rs       | 34 +++++++++
 challenge-256/roger-bell-west/scala/ch-1.scala   | 38 +++++++++++
 challenge-256/roger-bell-west/scala/ch-2.scala   | 36 ++++++++++
 challenge-256/roger-bell-west/tests.yaml         | 40 +++++++++++
 21 files changed, 778 insertions(+)
 create mode 100755 challenge-256/roger-bell-west/javascript/ch-1.js
 create mode 100755 challenge-256/roger-bell-west/javascript/ch-2.js
 create mode 100644 challenge-256/roger-bell-west/kotlin/ch-1.kt
 create mode 100644 challenge-256/roger-bell-west/kotlin/ch-2.kt
 create mode 100755 challenge-256/roger-bell-west/lua/ch-1.lua
 create mode 100755 challenge-256/roger-bell-west/lua/ch-2.lua
 create mode 100755 challenge-256/roger-bell-west/perl/ch-1.pl
 create mode 100755 challenge-256/roger-bell-west/perl/ch-2.pl
 create mode 100644 challenge-256/roger-bell-west/postscript/ch-1.ps
 create mode 100644 challenge-256/roger-bell-west/postscript/ch-2.ps
 create mode 100755 challenge-256/roger-bell-west/python/ch-1.py
 create mode 100755 challenge-256/roger-bell-west/python/ch-2.py
 create mode 100755 challenge-256/roger-bell-west/raku/ch-1.p6
 create mode 100755 challenge-256/roger-bell-west/raku/ch-2.p6
 create mode 100755 challenge-256/roger-bell-west/ruby/ch-1.rb
 create mode 100755 challenge-256/roger-bell-west/ruby/ch-2.rb
 create mode 100755 challenge-256/roger-bell-west/rust/ch-1.rs
 create mode 100755 challenge-256/roger-bell-west/rust/ch-2.rs
 create mode 100644 challenge-256/roger-bell-west/scala/ch-1.scala
 create mode 100644 challenge-256/roger-bell-west/scala/ch-2.scala
 create mode 100644 challenge-256/roger-bell-west/tests.yaml

diff --git a/challenge-256/roger-bell-west/javascript/ch-1.js b/challenge-256/roger-bell-west/javascript/ch-1.js
new file mode 100755
index 0000000000..487faea806
--- /dev/null
+++ b/challenge-256/roger-bell-west/javascript/ch-1.js
@@ -0,0 +1,36 @@
+#! /usr/bin/node
+
+"use strict"
+
+function maximumpairs(a) {
+    let n = 0;
+    let r = new Set;
+    for (let s of a) {
+        const t = s.split("").reverse().join("");
+        if (r.has(t)) {
+            n++;
+        } else {
+            r.add(s);
+        }
+    }
+    return n;
+}
+
+if (maximumpairs(['ab', 'de', 'ed', 'bc']) == 1) {
+  process.stdout.write("Pass");
+} else {
+  process.stdout.write("FAIL");
+}
+process.stdout.write(" ");
+if (maximumpairs(['aa', 'ba', 'cd', 'ed']) == 0) {
+  process.stdout.write("Pass");
+} else {
+  process.stdout.write("FAIL");
+}
+process.stdout.write(" ");
+if (maximumpairs(['uv', 'qp', 'st', 'vu', 'mn', 'pq']) == 2) {
+  process.stdout.write("Pass");
+} else {
+  process.stdout.write("FAIL");
+}
+process.stdout.write("\n");
diff --git a/challenge-256/roger-bell-west/javascript/ch-2.js b/challenge-256/roger-bell-west/javascript/ch-2.js
new file mode 100755
index 0000000000..62f3a05be9
--- /dev/null
+++ b/challenge-256/roger-bell-west/javascript/ch-2.js
@@ -0,0 +1,35 @@
+#! /usr/bin/node
+
+"use strict"
+
+function mergestrings(a, b) {
+    let out = "";
+    for (let i = 0; i < Math.max(a.length, b.length); i++) {
+        if (i <= a.length - 1) {
+            out += a.substring(i, i+1);
+        }
+        if (i <= b.length - 1) {
+            out += b.substring(i, i+1);
+        }
+    }
+    return out;
+}
+
+if (mergestrings('abcd', '1234') == 'a1b2c3d4') {
+  process.stdout.write("Pass");
+} else {
+  process.stdout.write("FAIL");
+}
+process.stdout.write(" ");
+if (mergestrings('abc', '12345') == 'a1b2c345') {
+  process.stdout.write("Pass");
+} else {
+  process.stdout.write("FAIL");
+}
+process.stdout.write(" ");
+if (mergestrings('abcde', '123') == 'a1b2c3de') {
+  process.stdout.write("Pass");
+} else {
+  process.stdout.write("FAIL");
+}
+process.stdout.write("\n");
diff --git a/challenge-256/roger-bell-west/kotlin/ch-1.kt b/challenge-256/roger-bell-west/kotlin/ch-1.kt
new file mode 100644
index 0000000000..bd433350bd
--- /dev/null
+++ b/challenge-256/roger-bell-west/kotlin/ch-1.kt
@@ -0,0 +1,36 @@
+fun maximumpairs(a: List<String>): Int {
+    var n = 0
+    var r = mutableSetOf<String>()
+    for (s in a) {
+        val t = s.reversed()
+        if (r.contains(t)) {
+            n += 1
+        } else {
+            r.add(s)
+        }
+    }
+    return n
+}
+
+fun main() {
+
+    if (maximumpairs(listOf("ab", "de", "ed", "bc")) == 1) {
+        print("Pass")
+    } else {
+        print("Fail")
+    }
+    print(" ")
+    if (maximumpairs(listOf("aa", "ba", "cd", "ed")) == 0) {
+        print("Pass")
+    } else {
+        print("Fail")
+    }
+    print(" ")
+    if (maximumpairs(listOf("uv", "qp", "st", "vu", "mn", "pq")) == 2) {
+        print("Pass")
+    } else {
+        print("Fail")
+    }
+    println("")
+
+}
diff --git a/challenge-256/roger-bell-west/kotlin/ch-2.kt b/challenge-256/roger-bell-west/kotlin/ch-2.kt
new file mode 100644
index 0000000000..d2dbdaa800
--- /dev/null
+++ b/challenge-256/roger-bell-west/kotlin/ch-2.kt
@@ -0,0 +1,37 @@
+import kotlin.math.max
+
+fun mergestrings(a: String, b: String): String {
+    var out = ""
+    for (i in 0 .. listOf(a.length, b.length).maxOrNull()!! - 1) {
+        if (i <= a.length - 1) {
+            out += a.substring(i, i+1)
+        }
+        if (i <= b.length - 1) {
+            out += b.substring(i, i+1)
+        }
+    }
+    return out
+}
+
+fun main() {
+
+    if (mergestrings("abcd", "1234") == "a1b2c3d4") {
+        print("Pass")
+    } else {
+        print("Fail")
+    }
+    print(" ")
+    if (mergestrings("abc", "12345") == "a1b2c345") {
+        print("Pass")
+    } else {
+        print("Fail")
+    }
+    print(" ")
+    if (mergestrings("abcde", "123") == "a1b2c3de") {
+        print("Pass")
+    } else {
+        print("Fail")
+    }
+    println("")
+
+}
diff --git a/challenge-256/roger-bell-west/lua/ch-1.lua b/challenge-256/roger-bell-west/lua/ch-1.lua
new file mode 100755
index 0000000000..b8316b4b7c
--- /dev/null
+++ b/challenge-256/roger-bell-west/lua/ch-1.lua
@@ -0,0 +1,37 @@
+#! /usr/bin/lua
+
+function maximumpairs(a)
+   local n = 0
+   local r = {}
+   for _, s in ipairs(a) do
+      local t = string.reverse(s)
+      if r[t] ~= nil then
+         n = n + 1
+      else
+         r[s] = true
+      end
+   end
+   return n
+end
+
+if maximumpairs({"ab", "de", "ed", "bc"}) == 1 then
+  io.write("Pass")
+else
+  io.write("FAIL")
+end
+io.write(" ")
+
+if maximumpairs({"aa", "ba", "cd", "ed"}) == 0 then
+  io.write("Pass")
+else
+  io.write("FAIL")
+end
+io.write(" ")
+
+if maximumpairs({"uv", "qp", "st", "vu", "mn", "pq"}) == 2 then
+  io.write("Pass")
+else
+  io.write("FAIL")
+end
+print("")
+
diff --git a/challenge-256/roger-bell-west/lua/ch-2.lua b/challenge-256/roger-bell-west/lua/ch-2.lua
new file mode 100755
index 0000000000..afbaa80653
--- /dev/null
+++ b/challenge-256/roger-bell-west/lua/ch-2.lua
@@ -0,0 +1,36 @@
+#! /usr/bin/lua
+
+function mergestrings(a, b)
+   local out = ""
+   for i = 1, math.max(string.len(a), string.len(b)) do
+      if i <= string.len(a) then
+         out = out .. string.sub(a, i, i)
+      end
+      if i <= string.len(b) then
+         out = out .. string.sub(b, i, i)
+      end
+   end
+   return out
+end
+
+if mergestrings("abcd", 1234) == "a1b2c3d4" then
+  io.write("Pass")
+else
+  io.write("FAIL")
+end
+io.write(" ")
+
+if mergestrings("abc", 12345) == "a1b2c345" then
+  io.write("Pass")
+else
+  io.write("FAIL")
+end
+io.write(" ")
+
+if mergestrings("abcde", 123) == "a1b2c3de" then
+  io.write("Pass")
+else
+  io.write("FAIL")
+end
+print("")
+
diff --git a/challenge-256/roger-bell-west/perl/ch-1.pl b/challenge-256/roger-bell-west/perl/ch-1.pl
new file mode 100755
index 0000000000..9ab01536ff
--- /dev/null
+++ b/challenge-256/roger-bell-west/perl/ch-1.pl
@@ -0,0 +1,25 @@
+#! /usr/bin/perl
+
+use strict;
+use warnings;
+use experimental 'signatures';
+
+use Test::More tests => 3;
+
+is(maximumpairs(['ab', 'de', 'ed', 'bc']), 1, 'example 1');
+is(maximumpairs(['aa', 'ba', 'cd', 'ed']), 0, 'example 2');
+is(maximumpairs(['uv', 'qp', 'st', 'vu', 'mn', 'pq']), 2, 'example 3');
+
+sub maximumpairs($a) {
+  my $n = 0;
+  my %r;
+  foreach my $s (@{$a}) {
+    my $t = reverse($s);
+    if (exists $r{$t}) {
+      $n++;
+    } else {
+      $r{$s} = 1;
+    }
+  }
+  return $n;
+}
diff --git a/challenge-256/roger-bell-west/perl/ch-2.pl b/challenge-256/roger-bell-west/perl/ch-2.pl
new file mode 100755
index 0000000000..44f704f864
--- /dev/null
+++ b/challenge-256/roger-bell-west/perl/ch-2.pl
@@ -0,0 +1,28 @@
+#! /usr/bin/perl
+
+use strict;
+use warnings;
+use experimental 'signatures';
+
+use Test::More tests => 3;
+
+is(mergestrings('abcd', 1234), 'a1b2c3d4', 'example 1');
+is(mergestrings('abc', 12345), 'a1b2c345', 'example 2');
+is(mergestrings('abcde', 123), 'a1b2c3de', 'example 3');
+
+use List::Util qw(max);
+
+sub mergestrings($a, $b) {
+  my @aa = split '', $a;
+  my @bb = split '', $b;
+  my $out;
+  foreach my $i (0 .. max($#aa, $#bb)) {
+    if ($i <= $#aa) {
+      $out .= $aa[$i];
+    }
+    if ($i <= $#bb) {
+      $out .= $bb[$i];
+    }
+  }
+  return $out;
+}
diff --git a/challenge-256/roger-bell-west/postscript/ch-1.ps b/challenge-256/roger-bell-west/postscript/ch-1.ps
new file mode 100644
index 0000000000..5af26ad4c7
--- /dev/null
+++ b/challenge-256/roger-bell-west/postscript/ch-1.ps
@@ -0,0 +1,87 @@
+%!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
+
+/s2a {
+    [ exch { } forall ]
+} bind def
+
+/test.start {
+    print (:) print
+    /test.pass 0 def
+    /test.count 0 def
+} bind def
+
+/a2s {
+    2 dict begin
+    /i exch def
+    i length dup string /o exch def
+    1 sub 0 exch 1 exch {
+        dup i 3 -1 roll get o 3 1 roll put
+    } for
+    o
+    end
+} bind def
+
+/reverse {
+    1 dict begin
+    dup length /l exch def
+    [ exch
+      aload pop
+      2 1 l {
+          -1 roll
+      } for
+    ]
+    end
+} 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
+
+/maximumpairs {
+    0 dict begin
+    /n 0 def
+    /r 0 dict def
+    {
+        /s exch def
+        /t s s2a reverse a2s def
+        r t known {
+            /n n 1 add def
+        } {
+            r s true put
+        } ifelse
+    } forall
+    n
+    end
+} bind def
+
+(maximumpairs) test.start
+[(ab) (de) (ed) (bc)] maximumpairs 1 eq test
+[(aa) (ba) (cd) (ed)] maximumpairs 0 eq test
+[(uv) (qp) (st) (vu) (mn) (pq)] maximumpairs 2 eq test
+test.end
diff --git a/challenge-256/roger-bell-west/postscript/ch-2.ps b/challenge-256/roger-bell-west/postscript/ch-2.ps
new file mode 100644
index 0000000000..cbe7bc8998
--- /dev/null
+++ b/challenge-256/roger-bell-west/postscript/ch-2.ps
@@ -0,0 +1,72 @@
+%!PS
+
+% begin included library code
+% see https://codeberg.org/Firedrake/postscript-libraries/
+/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
+
+/a2s {
+    2 dict begin
+    /i exch def
+    i length dup string /o exch def
+    1 sub 0 exch 1 exch {
+        dup i 3 -1 roll get o 3 1 roll put
+    } for
+    o
+    end
+} 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
+
+/mergestrings {
+    0 dict begin
+    /b exch def
+    /a exch def
+    [
+        0 1 a length b length max 1 sub {
+            /i exch def
+            i a length lt {
+                a i get
+            } if
+            i b length lt {
+                b i get
+            } if
+        } for
+    ] a2s
+    end
+} bind def
+
+(mergestrings) test.start
+(abcd) (1234) mergestrings (a1b2c3d4) eq test
+(abc) (12345) mergestrings (a1b2c345) eq test
+(abcde) (123) mergestrings (a1b2c3de) eq test
+test.end
diff --git a/challenge-256/roger-bell-west/python/ch-1.py b/challenge-256/roger-bell-west/python/ch-1.py
new file mode 100755
index 0000000000..41f87da92a
--- /dev/null
+++ b/challenge-256/roger-bell-west/python/ch-1.py
@@ -0,0 +1,27 @@
+#! /usr/bin/python3
+
+def maximumpairs(a):
+  n = 0
+  r = set()
+  for s in a:
+    t = s[::-1]
+    if t in r:
+      n += 1
+    else:
+      r.add(s)
+  return n
+
+import unittest
+
+class TestMaximumpairs(unittest.TestCase):
+
+  def test_ex1(self):
+    self.assertEqual(maximumpairs(["ab", "de", "ed", "bc"]), 1, 'example 1')
+
+  def test_ex2(self):
+    self.assertEqual(maximumpairs(["aa", "ba", "cd", "ed"]), 0, 'example 2')
+
+  def test_ex3(self):
+    self.assertEqual(maximumpairs(["uv", "qp", "st", "vu", "mn", "pq"]), 2, 'example 3')
+
+unittest.main()
diff --git a/challenge-256/roger-bell-west/python/ch-2.py b/challenge-256/roger-bell-west/python/ch-2.py
new file mode 100755
index 0000000000..ee02a99f35
--- /dev/null
+++ b/challenge-256/roger-bell-west/python/ch-2.py
@@ -0,0 +1,25 @@
+#! /usr/bin/python3
+
+def mergestrings(a, b):
+  out = ""
+  for i in range(max(len(a), len(b))):
+    if i < len(a):
+      out += a[i]
+    if i < len(b):
+      out += b[i]
+  return out
+
+import unittest
+
+class TestMergestrings(unittest.TestCase):
+
+  def test_ex1(self):
+    self.assertEqual(mergestrings("abcd", "1234"), "a1b2c3d4", 'example 1')
+
+  def test_ex2(self):
+    self.assertEqual(mergestrings("abc", "12345"), "a1b2c345", 'example 2')
+
+  def test_ex3(self):
+    self.assertEqual(mergestrings("abcde", "123"), "a1b2c3de", 'example 3')
+
+unittest.main()
diff --git a/challenge-256/roger-bell-west/raku/ch-1.p6 b/challenge-256/roger-bell-west/raku/ch-1.p6
new file mode 100755
index 0000000000..a889b25d78
--- /dev/null
+++ b/challenge-256/roger-bell-west/raku/ch-1.p6
@@ -0,0 +1,23 @@
+#! /usr/bin/raku
+
+use Test;
+
+plan 3;
+
+is(maximumpairs(['ab', 'de', 'ed', 'bc']), 1, 'example 1');
+is(maximumpairs(['aa', 'ba', 'cd', 'ed']), 0, 'example 2');
+is(maximumpairs(['uv', 'qp', 'st', 'vu', 'mn', 'pq']), 2, 'example 3');
+
+sub maximumpairs(@a) {
+    my $n = 0;
+    my $r = SetHash.new;
+    for @a -> $s {
+        my $t = $s.flip;
+        if ($r{$t}:exists) {
+            $n++;
+        } else {
+            $r{$s} = 1;
+        }
+    }
+    return $n;
+}
diff --git a/challenge-256/roger-bell-west/raku/ch-2.p6 b/challenge-256/roger-bell-west/raku/ch-2.p6
new file mode 100755
index 0000000000..4d806b107b
--- /dev/null
+++ b/challenge-256/roger-bell-west/raku/ch-2.p6
@@ -0,0 +1,24 @@
+#! /usr/bin/raku
+
+use Test;
+
+plan 3;
+
+is(mergestrings('abcd', 1234), 'a1b2c3d4', 'example 1');
+is(mergestrings('abc', 12345), 'a1b2c345', 'example 2');
+is(mergestrings('abcde', 123), 'a1b2c3de', 'example 3');
+
+sub mergestrings($a, $b) {
+    my @aa = $a.comb;
+    my @bb = $b.comb;
+    my $out;
+    for 0 .. max(@aa.end, @bb.end) -> $i {
+        if ($i <= @aa.end) {
+            $out ~= @aa[$i];
+        }
+        if ($i <= @bb.end) {
+            $out ~= @bb[$i];
+        }
+    }
+    return $out;
+}
diff --git a/challenge-256/roger-bell-west/ruby/ch-1.rb b/challenge-256/roger-bell-west/ruby/ch-1.rb
new file mode 100755
index 0000000000..447cbd195c
--- /dev/null
+++ b/challenge-256/roger-bell-west/ruby/ch-1.rb
@@ -0,0 +1,35 @@
+#! /usr/bin/ruby
+
+require 'set'
+
+def maximumpairs(a)
+  n = 0
+  r = Set.new
+  a.each do |s|
+    t = s.reverse
+    if r.include?(t) then
+      n += 1
+    else
+      r.add(s)
+    end
+  end
+  return n
+end
+
+require 'test/unit'
+
+class TestMaximumpairs < Test::Unit::TestCase
+
+  def test_ex1
+    assert_equal(1, maximumpairs(['ab', 'de', 'ed', 'bc']))
+  end
+
+  def test_ex2
+    assert_equal(0, maximumpairs(['aa', 'ba', 'cd', 'ed']))
+  end
+
+  def test_ex3
+    assert_equal(2, maximumpairs(['uv', 'qp', 'st', 'vu', 'mn', 'pq']))
+  end
+
+end
diff --git a/challenge-256/roger-bell-west/ruby/ch-2.rb b/challenge-256/roger-bell-west/ruby/ch-2.rb
new file mode 100755
index 0000000000..f85f21409f
--- /dev/null
+++ b/challenge-256/roger-bell-west/ruby/ch-2.rb
@@ -0,0 +1,34 @@
+#! /usr/bin/ruby
+
+def mergestrings(a, b)
+  aa = a.chars.to_a
+  bb = b.chars.to_a
+  out = ""
+  0.upto([a.length, b.length].max - 1) do |i|
+    if i < a.length then
+      out += aa[i]
+    end
+    if i < b.length then
+      out += bb[i]
+    end
+  end
+  return out
+end
+
+require 'test/unit'
+
+class TestMergestrings < Test::Unit::TestCase
+
+  def test_ex1
+    assert_equal('a1b2c3d4', mergestrings('abcd', '1234'))
+  end
+
+  def test_ex2
+    assert_equal('a1b2c345', mergestrings('abc', '12345'))
+  end
+
+  def test_ex3
+    assert_equal('a1b2c3de', mergestrings('abcde', '123'))
+  end
+
+end
diff --git a/challenge-256/roger-bell-west/rust/ch-1.rs b/challenge-256/roger-bell-west/rust/ch-1.rs
new file mode 100755
index 0000000000..810ce5bc64
--- /dev/null
+++ b/challenge-256/roger-bell-west/rust/ch-1.rs
@@ -0,0 +1,33 @@
+#! /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!(maximumpairs(vec!["ab", "de", "ed", "bc"]), 1);
+}
+
+#[test]
+fn test_ex2() {
+    assert_eq!(maximumpairs(vec!["aa", "ba", "cd", "ed"]), 0);
+}
+
+#[test]
+fn test_ex3() {
+    assert_eq!(maximumpairs(vec!["uv", "qp", "st", "vu", "mn", "pq"]), 2);
+}
+
+fn maximumpairs(a: Vec<&str>) -> u32 {
+    let mut n = 0;
+    let mut r: HashSet<String> = HashSet::new();
+    for s in a {
+        let t = s.chars().rev().collect::<String>();
+        if r.contains(&t) {
+            n += 1;
+        } else {
+            r.insert(s.to_string());
+        }
+    }
+    n
+}
diff --git a/challenge-256/roger-bell-west/rust/ch-2.rs b/challenge-256/roger-bell-west/rust/ch-2.rs
new file mode 100755
index 0000000000..59af687020
--- /dev/null
+++ b/challenge-256/roger-bell-west/rust/ch-2.rs
@@ -0,0 +1,34 @@
+#! /bin/sh
+//usr/bin/env rustc --test $0 -o ${0}x && ./${0}x --nocapture; rm -f ${0}x ; exit
+
+use std::cmp::max;
+
+#[test]
+fn test_ex1() {
+    assert_eq!(mergestrings("abcd", "1234"), "a1b2c3d4");
+}
+
+#[test]
+fn test_ex2() {
+    assert_eq!(mergestrings("abc", "12345"), "a1b2c345");
+}
+
+#[test]
+fn test_ex3() {
+    assert_eq!(mergestrings("abcde", "123"), "a1b2c3de");
+}
+
+fn mergestrings(a: &str, b: &str) -> String {
+    let aa = a.chars().collect::<Vec<char>>();
+    let bb = b.chars().collect::<Vec<char>>();
+    let mut out: String = String::new();
+    for i in 0 .. max(a.len(), b.len()) {
+        if i < a.len() {
+            out.push(aa[i]);
+        }
+        if i < b.len() {
+            out.push(bb[i]);
+        }
+    }
+    out
+}
diff --git a/challenge-256/roger-bell-west/scala/ch-1.scala b/challenge-256/roger-bell-west/scala/ch-1.scala
new file mode 100644
index 0000000000..82cc40f0ad
--- /dev/null
+++ b/challenge-256/roger-bell-west/scala/ch-1.scala
@@ -0,0 +1,38 @@
+import scala.collection.mutable
+
+object Maximumpairs {
+  def maximumpairs(a: List[String]): Int = {
+    var n = 0
+    var r = mutable.Set.empty[String]
+    for (s <- a) {
+      val t = s.reverse
+      if (r.contains(t)) {
+        n += 1
+      } else {
+        r += s
+      }
+    }
+    return n
+  }
+  def main(args: Array[String]) {
+    if (maximumpairs(List("ab", "de", "ed", "bc")) == 1) {
+      print("Pass")
+    } else {
+      print("Fail")
+    }
+    print(" ")
+    if (maximumpairs(List("aa", "ba", "cd", "ed")) == 0) {
+      print("Pass")
+    } else {
+      print("Fail")
+    }
+    print(" ")
+    if (maximumpairs(List("uv", "qp", "st", "vu", "mn", "pq")) == 2) {
+      print("Pass")
+    } else {
+      print("Fail")
+    }
+    println("")
+
+  }
+}
diff --git a/challenge-256/roger-bell-west/scala/ch-2.scala b/challenge-256/roger-bell-west/scala/ch-2.scala
new file mode 100644
index 0000000000..e97afb1a26
--- /dev/null
+++ b/challenge-256/roger-bell-west/scala/ch-2.scala
@@ -0,0 +1,36 @@
+
+object Mergestrings {
+  def mergestrings(a: String, b: String): String = {
+    var out = ""
+    for (i <- 0 to List(a.length, b.length).max) {
+      if (i <= a.length - 1) {
+        out += a.substring(i, i+1)
+      }
+      if (i <= b.length - 1) {
+        out += b.substring(i, i+1)
+      }
+    }
+    return out
+  }
+  def main(args: Array[String]) {
+    if (mergestrings("abcd", "1234") == "a1b2c3d4") {
+      print("Pass")
+    } else {
+      print("Fail")
+    }
+    print(" ")
+    if (mergestrings("abc", "12345") == "a1b2c345") {
+      print("Pass")
+    } else {
+      print("Fail")
+    }
+    print(" ")
+    if (mergestrings("abcde", "123") == "a1b2c3de") {
+      print("Pass")
+    } else {
+      print("Fail")
+    }
+    println("")
+
+  }
+}
diff --git a/challenge-256/roger-bell-west/tests.yaml b/challenge-256/roger-bell-west/tests.yaml
new file mode 100644
index 0000000000..4a44a7ad7b
--- /dev/null
+++ b/challenge-256/roger-bell-west/tests.yaml
@@ -0,0 +1,40 @@
+---
+ch-1:
+  - function: maximumpairs
+    arguments:
+      - ab
+      - de
+      - ed
+      - bc
+    result: 1
+  - arguments:
+      - aa
+      - ba
+      - cd
+      - ed
+    result: 0
+  - arguments:
+      - uv
+      - qp
+      - st
+      - vu
+      - mn
+      - pq
+    result: 2
+ch-2:
+  - function: mergestrings
+    multiarg: true
+    arguments:
+      - abcd
+      - "1234"
+    result: "a1b2c3d4"
+  - multiarg: true
+    arguments:
+      - abc
+      - "12345"
+    result: "a1b2c345"
+  - multiarg: true
+    arguments:
+      - abcde
+      - "123"
+    result: "a1b2c3de"
-- 
cgit