Merge pull request #11564 from Firedrake/rogerbw-challenge-308

RogerBW solutions for challenge no. 308

23 files changed, 760 insertions, 0 deletions

diff --git a/challenge-308/roger-bell-west/crystal/ch-1.cr b/challenge-308/roger-bell-west/crystal/ch-1.cr
new file mode 100755
index 0000000000..c6c72f0a73
--- /dev/null
+++ b/challenge-308/roger-bell-west/crystal/ch-1.cr
@@ -0,0 +1,20 @@
+#! /usr/bin/crystal
+
+def countcommon(a, b)
+  aa = Set.new(a)
+  bb = Set.new(b)
+  (aa & bb).size
+end
+
+require "spec"
+describe "countcommon" do
+  it "test_ex1" do
+    countcommon(["perl", "weekly", "challenge"], ["raku", "weekly", "challenge"]).should eq 2
+  end
+  it "test_ex2" do
+    countcommon(["perl", "raku", "python"], ["python", "java"]).should eq 1
+  end
+  it "test_ex3" do
+    countcommon(["guest", "contribution"], ["fun", "weekly", "challenge"]).should eq 0
+  end
+end
diff --git a/challenge-308/roger-bell-west/crystal/ch-2.cr b/challenge-308/roger-bell-west/crystal/ch-2.cr
new file mode 100755
index 0000000000..71ca4948d7
--- /dev/null
+++ b/challenge-308/roger-bell-west/crystal/ch-2.cr
@@ -0,0 +1,19 @@
+#! /usr/bin/crystal
+
+def decodexor(a, init)
+  ot = [ init ]
+  a.each do |v|
+    ot.push(ot[-1] ^ v)
+  end
+  ot
+end
+
+require "spec"
+describe "decodexor" do
+  it "test_ex1" do
+    decodexor([1, 2, 3], 1).should eq [1, 0, 2, 1]
+  end
+  it "test_ex2" do
+    decodexor([6, 2, 7, 3], 4).should eq [4, 2, 0, 7, 4]
+  end
+end
diff --git a/challenge-308/roger-bell-west/javascript/ch-1.js b/challenge-308/roger-bell-west/javascript/ch-1.js
new file mode 100755
index 0000000000..8ae2e45044
--- /dev/null
+++ b/challenge-308/roger-bell-west/javascript/ch-1.js
@@ -0,0 +1,29 @@
+#! /usr/bin/node
+
+"use strict"
+
+function countcommon(a, b) {
+    const aa = new Set(a);
+    const bb = new Set(b);
+    const intersect = new Set([...aa].filter(i => bb.has(i)));
+    return intersect.size;
+}
+
+if (countcommon(['perl', 'weekly', 'challenge'], ['raku', 'weekly', 'challenge']) == 2) {
+  process.stdout.write("Pass");
+} else {
+  process.stdout.write("FAIL");
+}
+process.stdout.write(" ");
+if (countcommon(['perl', 'raku', 'python'], ['python', 'java']) == 1) {
+  process.stdout.write("Pass");
+} else {
+  process.stdout.write("FAIL");
+}
+process.stdout.write(" ");
+if (countcommon(['guest', 'contribution'], ['fun', 'weekly', 'challenge']) == 0) {
+  process.stdout.write("Pass");
+} else {
+  process.stdout.write("FAIL");
+}
+process.stdout.write("\n");
diff --git a/challenge-308/roger-bell-west/javascript/ch-2.js b/challenge-308/roger-bell-west/javascript/ch-2.js
new file mode 100755
index 0000000000..2df8c21d87
--- /dev/null
+++ b/challenge-308/roger-bell-west/javascript/ch-2.js
@@ -0,0 +1,51 @@
+#! /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 decodexor(a, init) {
+    let out = [init];
+    for (let v of a) {
+        out.push(out[out.length-1] ^ v);
+    }
+    return out;
+}
+
+if (deepEqual(decodexor([1, 2, 3], 1), [1, 0, 2, 1])) {
+  process.stdout.write("Pass");
+} else {
+  process.stdout.write("FAIL");
+}
+process.stdout.write(" ");
+if (deepEqual(decodexor([6, 2, 7, 3], 4), [4, 2, 0, 7, 4])) {
+  process.stdout.write("Pass");
+} else {
+  process.stdout.write("FAIL");
+}
+process.stdout.write("\n");
diff --git a/challenge-308/roger-bell-west/kotlin/ch-1.kt b/challenge-308/roger-bell-west/kotlin/ch-1.kt
new file mode 100644
index 0000000000..b8ef34edb1
--- /dev/null
+++ b/challenge-308/roger-bell-west/kotlin/ch-1.kt
@@ -0,0 +1,28 @@
+fun countcommon(a: List<String>, b: List<String>): Int {
+    val aa = a.toSet()
+    val bb = b.toSet()
+    return aa.intersect(bb).toList().count()
+}
+
+fun main() {
+
+    if (countcommon(listOf("perl", "weekly", "challenge"), listOf("raku", "weekly", "challenge")) == 2) {
+        print("Pass")
+    } else {
+        print("Fail")
+    }
+    print(" ")
+    if (countcommon(listOf("perl", "raku", "python"), listOf("python", "java")) == 1) {
+        print("Pass")
+    } else {
+        print("Fail")
+    }
+    print(" ")
+    if (countcommon(listOf("guest", "contribution"), listOf("fun", "weekly", "challenge")) == 0) {
+        print("Pass")
+    } else {
+        print("Fail")
+    }
+    println("")
+
+}
diff --git a/challenge-308/roger-bell-west/kotlin/ch-2.kt b/challenge-308/roger-bell-west/kotlin/ch-2.kt
new file mode 100644
index 0000000000..5a05b0e322
--- /dev/null
+++ b/challenge-308/roger-bell-west/kotlin/ch-2.kt
@@ -0,0 +1,24 @@
+fun decodexor(a: List<Int>, nit: Int): List<Int> {
+    var out = ArrayList(listOf(nit))
+    for (v in a) {
+        out.add(out[out.size - 1] xor v)
+    }
+    return out.toList()
+}
+
+fun main() {
+
+    if (decodexor(listOf(1, 2, 3), 1) == listOf(1, 0, 2, 1)) {
+        print("Pass")
+    } else {
+        print("Fail")
+    }
+    print(" ")
+    if (decodexor(listOf(6, 2, 7, 3), 4) == listOf(4, 2, 0, 7, 4)) {
+        print("Pass")
+    } else {
+        print("Fail")
+    }
+    println("")
+
+}
diff --git a/challenge-308/roger-bell-west/lua/ch-1.lua b/challenge-308/roger-bell-west/lua/ch-1.lua
new file mode 100755
index 0000000000..de6796045b
--- /dev/null
+++ b/challenge-308/roger-bell-west/lua/ch-1.lua
@@ -0,0 +1,43 @@
+#! /usr/bin/lua
+
+function toset(a)
+   local p = {}
+   for _, c in ipairs(a) do
+      p[c] = true
+   end
+   return p
+end
+
+function countcommon(a, b)
+   local aa = toset(a)
+   local bb = toset(b)
+   local out = 0
+   for c, _ in pairs(aa) do
+      if bb[c] ~= nil then
+         out = out + 1
+      end
+   end
+   return out
+end
+
+if countcommon({"perl", "weekly", "challenge"}, {"raku", "weekly", "challenge"}) == 2 then
+  io.write("Pass")
+else
+  io.write("FAIL")
+end
+io.write(" ")
+
+if countcommon({"perl", "raku", "python"}, {"python", "java"}) == 1 then
+  io.write("Pass")
+else
+  io.write("FAIL")
+end
+io.write(" ")
+
+if countcommon({"guest", "contribution"}, {"fun", "weekly", "challenge"}) == 0 then
+  io.write("Pass")
+else
+  io.write("FAIL")
+end
+print("")
+
diff --git a/challenge-308/roger-bell-west/lua/ch-2.lua b/challenge-308/roger-bell-west/lua/ch-2.lua
new file mode 100755
index 0000000000..3febd0020e
--- /dev/null
+++ b/challenge-308/roger-bell-west/lua/ch-2.lua
@@ -0,0 +1,53 @@
+#! /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 decodexor(a, init)
+   local out = { init }
+   for _, v in ipairs(a) do
+      table.insert(out, out[#out] ~ v)
+   end
+   return out
+end
+
+if recursive_compare(decodexor({1, 2, 3}, 1), {1, 0, 2, 1}) then
+  io.write("Pass")
+else
+  io.write("FAIL")
+end
+io.write(" ")
+
+if recursive_compare(decodexor({6, 2, 7, 3}, 4), {4, 2, 0, 7, 4}) then
+  io.write("Pass")
+else
+  io.write("FAIL")
+end
+print("")
+
diff --git a/challenge-308/roger-bell-west/perl/ch-1.pl b/challenge-308/roger-bell-west/perl/ch-1.pl
new file mode 100755
index 0000000000..bfe5d6fccc
--- /dev/null
+++ b/challenge-308/roger-bell-west/perl/ch-1.pl
@@ -0,0 +1,17 @@
+#! /usr/bin/perl
+
+use strict;
+use warnings;
+use experimental 'signatures';
+
+use Test::More tests => 3;
+
+is(countcommon(['perl', 'weekly', 'challenge'], ['raku', 'weekly', 'challenge']), 2, 'example 1');
+is(countcommon(['perl', 'raku', 'python'], ['python', 'java']), 1, 'example 2');
+is(countcommon(['guest', 'contribution'], ['fun', 'weekly', 'challenge']), 0, 'example 3');
+
+sub countcommon($a, $b) {
+  my %aa = map {$_ => 1} @{$a};
+  my %bb = map {$_ => 1} @{$b};
+  scalar grep {exists $bb{$_}} keys %aa;
+}
diff --git a/challenge-308/roger-bell-west/perl/ch-2.pl b/challenge-308/roger-bell-west/perl/ch-2.pl
new file mode 100755
index 0000000000..d3510ac2fc
--- /dev/null
+++ b/challenge-308/roger-bell-west/perl/ch-2.pl
@@ -0,0 +1,18 @@
+#! /usr/bin/perl
+
+use strict;
+use warnings;
+use experimental 'signatures';
+
+use Test::More tests => 2;
+
+is_deeply(decodexor([1, 2, 3], 1), [1, 0, 2, 1], 'example 1');
+is_deeply(decodexor([6, 2, 7, 3], 4), [4, 2, 0, 7, 4], 'example 2');
+
+sub decodexor($a, $init) {
+  my @out = ($init);
+  foreach my $v (@{$a}) {
+    push @out, $out[-1] ^ $v;
+  }
+  \@out;
+}
diff --git a/challenge-308/roger-bell-west/postscript/ch-1.ps b/challenge-308/roger-bell-west/postscript/ch-1.ps
new file mode 100644
index 0000000000..bc2025fb24
--- /dev/null
+++ b/challenge-308/roger-bell-west/postscript/ch-1.ps
@@ -0,0 +1,78 @@
+%!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 {
+    /test.count test.count 1 add def
+    {
+        /test.pass test.pass 1 add def
+    } {
+        ( ) print
+        test.count (....) cvs print
+        (-fail) print
+    } ifelse
+} bind def
+
+/keys { % dict -> array of dict keys
+    [ exch
+      {
+          pop
+      } forall
+    ]
+} bind def
+
+/toset { % array -> dict of (value, true)
+    << exch
+       {
+           true
+       } forall
+    >>
+} 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
+
+/set.intersection {
+    4 dict begin
+    /s 0 dict def
+    /b exch def
+    /a exch def
+    a keys {
+        /k exch def
+        b k known {
+            s k true put
+        } if
+    } forall
+    s
+    end
+} bind def
+
+
+% end included library code
+
+/countcommon {
+    toset exch toset set.intersection length
+} bind def
+
+(countcommon) test.start
+[(perl) (weekly) (challenge)] [(raku) (weekly) (challenge)] countcommon 2 eq test
+[(perl) (raku) (python)] [(python) (java)] countcommon 1 eq test
+[(guest) (contribution)] [(fun) (weekly) (challenge)] countcommon 0 eq test
+test.end
diff --git a/challenge-308/roger-bell-west/postscript/ch-2.ps b/challenge-308/roger-bell-west/postscript/ch-2.ps
new file mode 100644
index 0000000000..4e943e4d08
--- /dev/null
+++ b/challenge-308/roger-bell-west/postscript/ch-2.ps
@@ -0,0 +1,109 @@
+%!PS
+
+% begin included library code
+% see https://codeberg.org/Firedrake/postscript-libraries/
+/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
+
+/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
+
+/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
+
+
+% end included library code
+
+/decodexor {
+    [ exch
+      3 -1 roll
+      {
+          exch dup 3 -1 roll xor
+      } forall
+    ]
+} bind def
+
+(decodexor) test.start
+[1 2 3] 1 decodexor [1 0 2 1] deepeq test
+[6 2 7 3] 4 decodexor [4 2 0 7 4] deepeq test
+test.end
diff --git a/challenge-308/roger-bell-west/python/ch-1.py b/challenge-308/roger-bell-west/python/ch-1.py
new file mode 100755
index 0000000000..639a3dbb4c
--- /dev/null
+++ b/challenge-308/roger-bell-west/python/ch-1.py
@@ -0,0 +1,21 @@
+#! /usr/bin/python3
+
+def countcommon(a, b):
+  aa = set(a)
+  bb = set(b)
+  return len(aa.intersection(bb))
+
+import unittest
+
+class TestCountcommon(unittest.TestCase):
+
+  def test_ex1(self):
+    self.assertEqual(countcommon(["perl", "weekly", "challenge"], ["raku", "weekly", "challenge"]), 2, 'example 1')
+
+  def test_ex2(self):
+    self.assertEqual(countcommon(["perl", "raku", "python"], ["python", "java"]), 1, 'example 2')
+
+  def test_ex3(self):
+    self.assertEqual(countcommon(["guest", "contribution"], ["fun", "weekly", "challenge"]), 0, 'example 3')
+
+unittest.main()
diff --git a/challenge-308/roger-bell-west/python/ch-2.py b/challenge-308/roger-bell-west/python/ch-2.py
new file mode 100755
index 0000000000..5ebb9fe738
--- /dev/null
+++ b/challenge-308/roger-bell-west/python/ch-2.py
@@ -0,0 +1,19 @@
+#! /usr/bin/python3
+
+def decodexor(a, init):
+  out = [init]
+  for v in a:
+    out.append(out[-1] ^ v)
+  return out
+
+import unittest
+
+class TestDecodexor(unittest.TestCase):
+
+  def test_ex1(self):
+    self.assertEqual(decodexor([1, 2, 3], 1), [1, 0, 2, 1], 'example 1')
+
+  def test_ex2(self):
+    self.assertEqual(decodexor([6, 2, 7, 3], 4), [4, 2, 0, 7, 4], 'example 2')
+
+unittest.main()
diff --git a/challenge-308/roger-bell-west/raku/ch-1.p6 b/challenge-308/roger-bell-west/raku/ch-1.p6
new file mode 100755
index 0000000000..3cea509b34
--- /dev/null
+++ b/challenge-308/roger-bell-west/raku/ch-1.p6
@@ -0,0 +1,15 @@
+#! /usr/bin/raku
+
+use Test;
+
+plan 3;
+
+is(countcommon(['perl', 'weekly', 'challenge'], ['raku', 'weekly', 'challenge']), 2, 'example 1');
+is(countcommon(['perl', 'raku', 'python'], ['python', 'java']), 1, 'example 2');
+is(countcommon(['guest', 'contribution'], ['fun', 'weekly', 'challenge']), 0, 'example 3');
+
+sub countcommon(@a, @b) {
+  my %aa = set(@a);
+  my %bb = set(@b);
+  (%aa (&) %bb).elems;
+}
diff --git a/challenge-308/roger-bell-west/raku/ch-2.p6 b/challenge-308/roger-bell-west/raku/ch-2.p6
new file mode 100755
index 0000000000..d6d6d0cf5a
--- /dev/null
+++ b/challenge-308/roger-bell-west/raku/ch-2.p6
@@ -0,0 +1,16 @@
+#! /usr/bin/raku
+
+use Test;
+
+plan 2;
+
+is-deeply(decodexor([1, 2, 3], 1), [1, 0, 2, 1], 'example 1');
+is-deeply(decodexor([6, 2, 7, 3], 4), [4, 2, 0, 7, 4], 'example 2');
+
+sub decodexor(@a, $init) {
+  my @out = [$init];
+  for @a -> $v {
+    @out.push(@out[*-1] +^ $v);
+  }
+  @out;
+}
diff --git a/challenge-308/roger-bell-west/ruby/ch-1.rb b/challenge-308/roger-bell-west/ruby/ch-1.rb
new file mode 100755
index 0000000000..9ce78fc6f9
--- /dev/null
+++ b/challenge-308/roger-bell-west/ruby/ch-1.rb
@@ -0,0 +1,27 @@
+#! /usr/bin/ruby
+
+require 'set'
+
+def countcommon(a, b)
+  aa = Set.new(a)
+  bb = Set.new(b)
+  (aa & bb).length
+end
+
+require 'test/unit'
+
+class TestCountcommon < Test::Unit::TestCase
+
+  def test_ex1
+    assert_equal(2, countcommon(['perl', 'weekly', 'challenge'], ['raku', 'weekly', 'challenge']))
+  end
+
+  def test_ex2
+    assert_equal(1, countcommon(['perl', 'raku', 'python'], ['python', 'java']))
+  end
+
+  def test_ex3
+    assert_equal(0, countcommon(['guest', 'contribution'], ['fun', 'weekly', 'challenge']))
+  end
+
+end
diff --git a/challenge-308/roger-bell-west/ruby/ch-2.rb b/challenge-308/roger-bell-west/ruby/ch-2.rb
new file mode 100755
index 0000000000..6306525136
--- /dev/null
+++ b/challenge-308/roger-bell-west/ruby/ch-2.rb
@@ -0,0 +1,23 @@
+#! /usr/bin/ruby
+
+def decodexor(a, init)
+  out = [ init ]
+  a.each do |v|
+    out.push(out[-1] ^ v)
+  end
+  out
+end
+
+require 'test/unit'
+
+class TestDecodexor < Test::Unit::TestCase
+
+  def test_ex1
+    assert_equal([1, 0, 2, 1], decodexor([1, 2, 3], 1))
+  end
+
+  def test_ex2
+    assert_equal([4, 2, 0, 7, 4], decodexor([6, 2, 7, 3], 4))
+  end
+
+end
diff --git a/challenge-308/roger-bell-west/rust/ch-1.rs b/challenge-308/roger-bell-west/rust/ch-1.rs
new file mode 100755
index 0000000000..33fb782564
--- /dev/null
+++ b/challenge-308/roger-bell-west/rust/ch-1.rs
@@ -0,0 +1,26 @@
+#! /bin/sh
+//usr/bin/env rustc --test $0 -o ${0}x && ./${0}x --nocapture; rm -f ${0}x ; exit
+
+use std::collections::HashSet;
+use std::iter::FromIterator;
+
+#[test]
+fn test_ex1() {
+    assert_eq!(countcommon(vec!["perl", "weekly", "challenge"], vec!["raku", "weekly", "challenge"]), 2);
+}
+
+#[test]
+fn test_ex2() {
+    assert_eq!(countcommon(vec!["perl", "raku", "python"], vec!["python", "java"]), 1);
+}
+
+#[test]
+fn test_ex3() {
+    assert_eq!(countcommon(vec!["guest", "contribution"], vec!["fun", "weekly", "challenge"]), 0);
+}
+
+fn countcommon(a: Vec<&str>, b: Vec<&str>) -> usize {
+    let aa: HashSet<&str> = HashSet::from_iter(a.into_iter());
+    let bb: HashSet<&str> = HashSet::from_iter(b.into_iter());
+    aa.intersection(&bb).count()
+}
diff --git a/challenge-308/roger-bell-west/rust/ch-2.rs b/challenge-308/roger-bell-west/rust/ch-2.rs
new file mode 100755
index 0000000000..9aa11720e2
--- /dev/null
+++ b/challenge-308/roger-bell-west/rust/ch-2.rs
@@ -0,0 +1,20 @@
+#! /bin/sh
+//usr/bin/env rustc --test $0 -o ${0}x && ./${0}x --nocapture; rm -f ${0}x ; exit
+
+#[test]
+fn test_ex1() {
+    assert_eq!(decodexor(vec![1, 2, 3], 1), vec![1, 0, 2, 1]);
+}
+
+#[test]
+fn test_ex2() {
+    assert_eq!(decodexor(vec![6, 2, 7, 3], 4), vec![4, 2, 0, 7, 4]);
+}
+
+fn decodexor(a: Vec<u32>, init: u32) -> Vec<u32> {
+    let mut out = vec![init];
+    for v in a {
+        out.push(out[out.len() - 1] ^ v);
+    }
+    out
+}
diff --git a/challenge-308/roger-bell-west/scala/ch-1.scala b/challenge-308/roger-bell-west/scala/ch-1.scala
new file mode 100644
index 0000000000..b3ab361288
--- /dev/null
+++ b/challenge-308/roger-bell-west/scala/ch-1.scala
@@ -0,0 +1,29 @@
+
+object Countcommon {
+  def countcommon(a: List[String], b: List[String]): Int = {
+    val aa = a.toSet
+    val bb = b.toSet
+    return aa.intersect(bb).toList.size
+  }
+  def main(args: Array[String]) {
+    if (countcommon(List("perl", "weekly", "challenge"), List("raku", "weekly", "challenge")) == 2) {
+      print("Pass")
+    } else {
+      print("Fail")
+    }
+    print(" ")
+    if (countcommon(List("perl", "raku", "python"), List("python", "java")) == 1) {
+      print("Pass")
+    } else {
+      print("Fail")
+    }
+    print(" ")
+    if (countcommon(List("guest", "contribution"), List("fun", "weekly", "challenge")) == 0) {
+      print("Pass")
+    } else {
+      print("Fail")
+    }
+    println("")
+
+  }
+}
\ No newline at end of file
diff --git a/challenge-308/roger-bell-west/scala/ch-2.scala b/challenge-308/roger-bell-west/scala/ch-2.scala
new file mode 100644
index 0000000000..67b574aabf
--- /dev/null
+++ b/challenge-308/roger-bell-west/scala/ch-2.scala
@@ -0,0 +1,27 @@
+import scala.collection.mutable.ListBuffer
+
+object Decodexor {
+  def decodexor(a: List[Int], nit: Int): List[Int] = {
+    var out = new ListBuffer[Int]
+    out += nit
+    for (v <- a) {
+      out += (out(out.size - 1) ^ v)
+    }
+    return out.toList
+  }
+  def main(args: Array[String]) {
+    if (decodexor(List(1, 2, 3), 1) == List(1, 0, 2, 1)) {
+      print("Pass")
+    } else {
+      print("Fail")
+    }
+    print(" ")
+    if (decodexor(List(6, 2, 7, 3), 4) == List(4, 2, 0, 7, 4)) {
+      print("Pass")
+    } else {
+      print("Fail")
+    }
+    println("")
+
+  }
+}
\ No newline at end of file
diff --git a/challenge-308/roger-bell-west/tests.json b/challenge-308/roger-bell-west/tests.json
new file mode 100644
index 0000000000..c6d5a7228c
--- /dev/null
+++ b/challenge-308/roger-bell-west/tests.json
@@ -0,0 +1,48 @@
+{
+    "ch-1" : [
+        {
+            "function" : "countcommon",
+            "multiarg" : true,
+            "arguments" : [
+                [ "perl", "weekly", "challenge" ],
+                [ "raku", "weekly", "challenge" ]
+            ],
+            "result" : 2
+        },
+        {
+            "multiarg" : true,
+            "arguments" : [
+                [ "perl", "raku", "python" ],
+                [ "python", "java" ]
+            ],
+            "result" : 1
+        },
+        {
+            "multiarg" : true,
+            "arguments" : [
+                [ "guest", "contribution" ],
+                [ "fun", "weekly", "challenge" ]
+            ],
+            "result" : 0
+        }
+    ],
+    "ch-2" : [
+        {
+            "function" : "decodexor",
+            "multiarg" : true,
+            "arguments" : [
+                [ 1, 2, 3 ],
+                1
+            ],
+            "result" : [ 1, 0, 2, 1 ]
+        },
+        {
+            "multiarg" : true,
+            "arguments" : [
+                [ 6, 2, 7, 3 ],
+                4
+            ],
+            "result" : [ 4, 2, 0, 7, 4 ]
+        }
+    ]
+}