RogerBW solutions for challenge no. 306

23 files changed, 892 insertions, 0 deletions

diff --git a/challenge-306/roger-bell-west/crystal/ch-1.cr b/challenge-306/roger-bell-west/crystal/ch-1.cr
new file mode 100755
index 0000000000..572acd56aa
--- /dev/null
+++ b/challenge-306/roger-bell-west/crystal/ch-1.cr
@@ -0,0 +1,24 @@
+#! /usr/bin/crystal
+
+def oddsum(a)
+  out = a.sum
+  l = 3
+  while l <= a.size
+    a.each_cons(l) do |s|
+      out += s.sum
+    end
+    l += 2
+  end
+  out
+end
+
+require "spec"
+
+describe "oddsum" do
+  it "test_ex1" do
+    oddsum([2, 5, 3, 6, 4]).should eq 77
+  end
+  it "test_ex2" do
+    oddsum([1, 3]).should eq 4
+  end
+end
diff --git a/challenge-306/roger-bell-west/crystal/ch-2.cr b/challenge-306/roger-bell-west/crystal/ch-2.cr
new file mode 100755
index 0000000000..d97d24c278
--- /dev/null
+++ b/challenge-306/roger-bell-west/crystal/ch-2.cr
@@ -0,0 +1,29 @@
+#! /usr/bin/crystal
+
+def lastelement(a)
+  b = a
+  while true
+    b.sort!
+    f = b.pop
+    s = b.pop
+    if f > s
+      b.push(f - s)
+    end
+    if b.size == 0
+      return 0
+    end
+    if b.size == 1
+      return b[0]
+    end
+  end
+end
+
+require "spec"
+describe "lastelement" do
+  it "test_ex1" do
+    lastelement([3, 8, 5, 2, 9, 2]).should eq 1
+  end
+  it "test_ex2" do
+    lastelement([3, 2, 5]).should eq 0
+  end
+end
diff --git a/challenge-306/roger-bell-west/javascript/ch-1.js b/challenge-306/roger-bell-west/javascript/ch-1.js
new file mode 100755
index 0000000000..d0875522fb
--- /dev/null
+++ b/challenge-306/roger-bell-west/javascript/ch-1.js
@@ -0,0 +1,37 @@
+#! /usr/bin/node
+
+"use strict"
+
+// 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 oddsum(a) {
+    let out = a.reduce((x, y) => x + y);
+    let l = 3;
+    while (l <= a.length) {
+        for (let s of toWindows(a, l)) {
+            out += s.reduce((x, y) => x + y);
+        }
+        l += 2;
+    }
+    return out;
+}
+
+if (oddsum([2, 5, 3, 6, 4]) == 77) {
+  process.stdout.write("Pass");
+} else {
+  process.stdout.write("FAIL");
+}
+process.stdout.write(" ");
+if (oddsum([1, 3]) == 4) {
+  process.stdout.write("Pass");
+} else {
+  process.stdout.write("FAIL");
+}
+process.stdout.write("\n");
diff --git a/challenge-306/roger-bell-west/javascript/ch-2.js b/challenge-306/roger-bell-west/javascript/ch-2.js
new file mode 100755
index 0000000000..910ba82fa0
--- /dev/null
+++ b/challenge-306/roger-bell-west/javascript/ch-2.js
@@ -0,0 +1,36 @@
+#! /usr/bin/node
+
+"use strict"
+
+function lastelement(a) {
+    let b = [...a];
+    while (true) {
+        b.sort(function(aa, bb) {
+        return aa - bb;
+        });
+        let f = b.pop();
+        let s = b.pop();
+        if (f > s) {
+            b.push(f - s);
+        }
+        if (b.length == 0) {
+            return 0;
+        }
+        if (b.length == 1) {
+            return b[0];
+        }
+    }
+}
+
+if (lastelement([3, 8, 5, 2, 9, 2]) == 1) {
+  process.stdout.write("Pass");
+} else {
+  process.stdout.write("FAIL");
+}
+process.stdout.write(" ");
+if (lastelement([3, 2, 5]) == 0) {
+  process.stdout.write("Pass");
+} else {
+  process.stdout.write("FAIL");
+}
+process.stdout.write("\n");
diff --git a/challenge-306/roger-bell-west/kotlin/ch-1.kt b/challenge-306/roger-bell-west/kotlin/ch-1.kt
new file mode 100644
index 0000000000..d104603c62
--- /dev/null
+++ b/challenge-306/roger-bell-west/kotlin/ch-1.kt
@@ -0,0 +1,28 @@
+fun oddsum(a: List<Int>): Int {
+    var out = a.sum()
+    var l = 3
+    while (l <= a.size) {
+        for (s in a.windowed(l)) {
+            out += s.sum()
+        }
+        l += 2
+    }
+    return out
+}
+
+fun main() {
+
+    if (oddsum(listOf(2, 5, 3, 6, 4)) == 77) {
+        print("Pass")
+    } else {
+        print("Fail")
+    }
+    print(" ")
+    if (oddsum(listOf(1, 3)) == 4) {
+        print("Pass")
+    } else {
+        print("Fail")
+    }
+    println("")
+
+}
diff --git a/challenge-306/roger-bell-west/kotlin/ch-2.kt b/challenge-306/roger-bell-west/kotlin/ch-2.kt
new file mode 100644
index 0000000000..be572837bf
--- /dev/null
+++ b/challenge-306/roger-bell-west/kotlin/ch-2.kt
@@ -0,0 +1,34 @@
+fun lastelement(a: List<Int>): Int {
+    var b = ArrayList(a)
+    while (true) {
+        b.sort()
+        var f = b.removeLast()
+        var s = b.removeLast()
+        if (f > s) {
+            b.add(f - s)
+        }
+        if (b.size == 0) {
+            return 0
+        }
+        if (b.size == 1) {
+            return b[0]
+        }
+    }
+}
+
+fun main() {
+
+    if (lastelement(listOf(3, 8, 5, 2, 9, 2)) == 1) {
+        print("Pass")
+    } else {
+        print("Fail")
+    }
+    print(" ")
+    if (lastelement(listOf(3, 2, 5)) == 0) {
+        print("Pass")
+    } else {
+        print("Fail")
+    }
+    println("")
+
+}
diff --git a/challenge-306/roger-bell-west/lua/ch-1.lua b/challenge-306/roger-bell-west/lua/ch-1.lua
new file mode 100755
index 0000000000..1ab8b6d95c
--- /dev/null
+++ b/challenge-306/roger-bell-west/lua/ch-1.lua
@@ -0,0 +1,43 @@
+#! /usr/bin/lua
+
+function windowed(a, n)
+   local out = {}
+   for i = 1, #a - n + 1 do
+      local t = {}
+      for j = i, i + n - 1 do
+         table.insert(t, a[j])
+      end
+      table.insert(out, t)
+   end
+   return out
+end
+
+function oddsum(a)
+   local out = 0
+   local l = 1
+   while l <= #a do
+      for _i, s in ipairs(windowed(a, l)) do
+         for _j, nn in ipairs(s) do
+            out = out + nn
+         end
+      end
+      l = l + 2
+   end
+   return out
+end
+   
+
+if oddsum({2, 5, 3, 6, 4}) == 77 then
+  io.write("Pass")
+else
+  io.write("FAIL")
+end
+io.write(" ")
+
+if oddsum({1, 3}) == 4 then
+  io.write("Pass")
+else
+  io.write("FAIL")
+end
+print("")
+
diff --git a/challenge-306/roger-bell-west/lua/ch-2.lua b/challenge-306/roger-bell-west/lua/ch-2.lua
new file mode 100755
index 0000000000..1d3179e5cb
--- /dev/null
+++ b/challenge-306/roger-bell-west/lua/ch-2.lua
@@ -0,0 +1,34 @@
+#! /usr/bin/lua
+
+function lastelement(a)
+   local b = a
+   while true do
+      table.sort(b)
+      local f = table.remove(b, #b)
+      local s = table.remove(b, #b)
+      if f > s then
+         table.insert(b, f - s)
+      end
+      if #b == 0 then
+         return 0
+      end
+      if #b == 1 then
+         return b[1]
+      end
+   end
+end
+
+if lastelement({3, 8, 5, 2, 9, 2}) == 1 then
+  io.write("Pass")
+else
+  io.write("FAIL")
+end
+io.write(" ")
+
+if lastelement({3, 2, 5}) == 0 then
+  io.write("Pass")
+else
+  io.write("FAIL")
+end
+print("")
+
diff --git a/challenge-306/roger-bell-west/perl/ch-1.pl b/challenge-306/roger-bell-west/perl/ch-1.pl
new file mode 100755
index 0000000000..21851fdb10
--- /dev/null
+++ b/challenge-306/roger-bell-west/perl/ch-1.pl
@@ -0,0 +1,28 @@
+#! /usr/bin/perl
+
+use strict;
+use warnings;
+use experimental 'signatures';
+
+use Test::More tests => 2;
+
+is(oddsum([2, 5, 3, 6, 4]), 77, 'example 1');
+is(oddsum([1, 3]), 4, 'example 2');
+
+use List::Util qw(sum);
+use List::MoreUtils qw(slideatatime);
+
+sub oddsum($a) {
+  my $out = sum(@{$a});
+  my $l = 3;
+  while ($l <= scalar @{$a}) {
+    my $dd = slideatatime 1, $l, @{$a};
+    while (my @s = $dd->()) {
+      if (scalar @s == $l) {
+        $out += sum(@s);
+      }
+    }
+    $l += 2;
+  }
+  $out;
+}
diff --git a/challenge-306/roger-bell-west/perl/ch-2.pl b/challenge-306/roger-bell-west/perl/ch-2.pl
new file mode 100755
index 0000000000..fca3c565bd
--- /dev/null
+++ b/challenge-306/roger-bell-west/perl/ch-2.pl
@@ -0,0 +1,28 @@
+#! /usr/bin/perl
+
+use strict;
+use warnings;
+use experimental 'signatures';
+
+use Test::More tests => 2;
+
+is(lastelement([3, 8, 5, 2, 9, 2]), 1, 'example 1');
+is(lastelement([3, 2, 5]), 0, 'example 2');
+
+sub lastelement($a) {
+  my @b = @{$a};
+  while (1) {
+    @b = sort {$::a <=> $::b} @b;
+    my $f = pop @b;
+    my $s = pop @b;
+    if ($f > $s) {
+      push @b, $f - $s;
+    }
+    if (scalar @b == 0) {
+      return 0;
+    }
+    if (scalar @b == 1) {
+      return $b[0];
+    }
+  }
+}
diff --git a/challenge-306/roger-bell-west/postscript/ch-1.ps b/challenge-306/roger-bell-west/postscript/ch-1.ps
new file mode 100644
index 0000000000..9c53e9779c
--- /dev/null
+++ b/challenge-306/roger-bell-west/postscript/ch-1.ps
@@ -0,0 +1,90 @@
+%!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
+
+/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
+
+/rotor {
+    5 dict begin
+    /delta exch def
+    /size exch def
+    dup length /len exch def
+    /ar exch def
+    /ix 0 def
+    [
+        {
+            ix size add len gt {
+                exit
+            } if
+            ar ix size getinterval
+            /ix ix size delta add add def
+        } loop
+    ]
+    end
+} 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
+
+
+% end included library code
+
+/oddsum {
+    0 dict begin
+    /a exch def
+    a { add } reduce
+    /l 3 def
+    {
+        l a length gt {
+            exit
+        } if
+        a l dup 1 sub neg rotor {
+            { add } reduce add
+        } forall
+        /l l 2 add def
+    } loop
+    end
+} bind def
+
+(oddsum) test.start
+[2 5 3 6 4] oddsum 77 eq test
+[1 3] oddsum 4 eq test
+test.end
diff --git a/challenge-306/roger-bell-west/postscript/ch-2.ps b/challenge-306/roger-bell-west/postscript/ch-2.ps
new file mode 100644
index 0000000000..2769a698ce
--- /dev/null
+++ b/challenge-306/roger-bell-west/postscript/ch-2.ps
@@ -0,0 +1,163 @@
+%!PS
+
+% begin included library code
+% see https://codeberg.org/Firedrake/postscript-libraries/
+/apop.right { % [a b c] -> [a b] c
+    [ exch aload length 1 add 1 roll ] exch
+} 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
+
+/apush.right { % [a b] c -> [a b c]
+    exch
+    [ exch aload length 2 add -1 roll ]
+} 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
+
+/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.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 {
+    { quicksort.cmp } quicksort.with_comparator
+} 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
+
+/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
+
+/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
+
+
+% end included library code
+
+/lastelement {
+    0 dict begin
+    /b exch def
+    {
+        /b b quicksort def
+        /b
+        b apop.right /f exch def
+        apop.right /s exch def
+        def
+        f s gt {
+            /b b f s sub apush.right def
+        } if
+        b length 0 eq {
+            0
+            exit
+        } if
+        b length 1 eq {
+            b 0 get
+            exit
+        } if
+    } loop
+    end
+} bind def
+
+(lastelement) test.start
+[3 8 5 2 9 2] lastelement 1 eq test
+[3 2 5] lastelement 0 eq test
+test.end
diff --git a/challenge-306/roger-bell-west/python/ch-1.py b/challenge-306/roger-bell-west/python/ch-1.py
new file mode 100755
index 0000000000..77fabf743a
--- /dev/null
+++ b/challenge-306/roger-bell-west/python/ch-1.py
@@ -0,0 +1,36 @@
+#! /usr/bin/python3
+
+import collections
+from itertools import 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 oddsum(a):
+  out = sum(a)
+  l = 3
+  while l <= len(a):
+    for s in sliding_window(a, l):
+      out += sum(s)
+    l += 2
+  return out
+
+import unittest
+
+class TestOddsum(unittest.TestCase):
+
+  def test_ex1(self):
+    self.assertEqual(oddsum([2, 5, 3, 6, 4]), 77, 'example 1')
+
+  def test_ex2(self):
+    self.assertEqual(oddsum([1, 3]), 4, 'example 2')
+
+unittest.main()
diff --git a/challenge-306/roger-bell-west/python/ch-2.py b/challenge-306/roger-bell-west/python/ch-2.py
new file mode 100755
index 0000000000..d16bb157a1
--- /dev/null
+++ b/challenge-306/roger-bell-west/python/ch-2.py
@@ -0,0 +1,26 @@
+#! /usr/bin/python3
+
+def lastelement(a):
+  b = a
+  while True:
+    b.sort()
+    f = b.pop()
+    s = b.pop()
+    if f > s:
+      b.append(f - s)
+    if len(b) == 0:
+      return 0
+    if len(b) == 1:
+      return b[0]
+
+import unittest
+
+class TestLastelement(unittest.TestCase):
+
+  def test_ex1(self):
+    self.assertEqual(lastelement([3, 8, 5, 2, 9, 2]), 1, 'example 1')
+
+  def test_ex2(self):
+    self.assertEqual(lastelement([3, 2, 5]), 0, 'example 2')
+
+unittest.main()
diff --git a/challenge-306/roger-bell-west/raku/ch-1.p6 b/challenge-306/roger-bell-west/raku/ch-1.p6
new file mode 100755
index 0000000000..17125cf99e
--- /dev/null
+++ b/challenge-306/roger-bell-west/raku/ch-1.p6
@@ -0,0 +1,20 @@
+#! /usr/bin/raku
+
+use Test;
+
+plan 2;
+
+is(oddsum([2, 5, 3, 6, 4]), 77, 'example 1');
+is(oddsum([1, 3]), 4, 'example 2');
+
+sub oddsum(@a) {
+    my $out = @a.sum;
+    my $l = 3;
+    while ($l <= @a.elems) {
+        for @a.rotor($l => -($l - 1)) -> @s {
+            $out += @s.sum;
+        }
+        $l += 2;
+    }
+    $out;
+}
diff --git a/challenge-306/roger-bell-west/raku/ch-2.p6 b/challenge-306/roger-bell-west/raku/ch-2.p6
new file mode 100755
index 0000000000..220cce8e2d
--- /dev/null
+++ b/challenge-306/roger-bell-west/raku/ch-2.p6
@@ -0,0 +1,26 @@
+#! /usr/bin/raku
+
+use Test;
+
+plan 2;
+
+is(lastelement([3, 8, 5, 2, 9, 2]), 1, 'example 1');
+is(lastelement([3, 2, 5]), 0, 'example 2');
+
+sub lastelement(@a) {
+    my @b = @a;
+    loop {
+        @b = @b.sort({$^a <=> $^b});
+        my $f = @b.pop;
+        my $s = @b.pop;
+        if ($f > $s) {
+            @b.push($f - $s);
+        }
+        if (@b.elems == 0) {
+            return 0;
+        }
+        if (@b.elems == 1) {
+            return @b[0];
+        }
+    }
+}
diff --git a/challenge-306/roger-bell-west/ruby/ch-1.rb b/challenge-306/roger-bell-west/ruby/ch-1.rb
new file mode 100755
index 0000000000..6fd8414f3f
--- /dev/null
+++ b/challenge-306/roger-bell-west/ruby/ch-1.rb
@@ -0,0 +1,27 @@
+#! /usr/bin/ruby
+
+def oddsum(a)
+  out = a.sum
+  l = 3
+  while l <= a.length do
+    a.each_cons(l) do |s|
+      out += s.sum
+    end
+    l += 2
+  end
+  out
+end
+
+require 'test/unit'
+
+class TestOddsum < Test::Unit::TestCase
+
+  def test_ex1
+    assert_equal(77, oddsum([2, 5, 3, 6, 4]))
+  end
+
+  def test_ex2
+    assert_equal(4, oddsum([1, 3]))
+  end
+
+end
diff --git a/challenge-306/roger-bell-west/ruby/ch-2.rb b/challenge-306/roger-bell-west/ruby/ch-2.rb
new file mode 100755
index 0000000000..be6acca74d
--- /dev/null
+++ b/challenge-306/roger-bell-west/ruby/ch-2.rb
@@ -0,0 +1,33 @@
+#! /usr/bin/ruby
+
+def lastelement(a)
+  b = a
+  while true do
+    b.sort!
+    f = b.pop
+    s = b.pop
+    if f > s
+      b.push(f - s)
+    end
+    if b.length == 0
+      return 0
+    end
+    if b.length == 1
+      return b[0]
+    end
+  end
+end
+
+require 'test/unit'
+
+class TestLastelement < Test::Unit::TestCase
+
+  def test_ex1
+    assert_equal(1, lastelement([3, 8, 5, 2, 9, 2]))
+  end
+
+  def test_ex2
+    assert_equal(0, lastelement([3, 2, 5]))
+  end
+
+end
diff --git a/challenge-306/roger-bell-west/rust/ch-1.rs b/challenge-306/roger-bell-west/rust/ch-1.rs
new file mode 100755
index 0000000000..b5de3195de
--- /dev/null
+++ b/challenge-306/roger-bell-west/rust/ch-1.rs
@@ -0,0 +1,25 @@
+#! /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!(oddsum(vec![2, 5, 3, 6, 4]), 77);
+}
+
+#[test]
+fn test_ex2() {
+    assert_eq!(oddsum(vec![1, 3]), 4);
+}
+
+fn oddsum(a: Vec<u32>) -> u32 {
+    let mut out: u32 = a.iter().sum();
+    let mut l = 3;
+    while l <= a.len() {
+        for s in a.windows(l) {
+            out += s.into_iter().sum::<u32>();
+        }
+        l += 2;
+    }
+    out
+}
+
diff --git a/challenge-306/roger-bell-west/rust/ch-2.rs b/challenge-306/roger-bell-west/rust/ch-2.rs
new file mode 100755
index 0000000000..db6bf31275
--- /dev/null
+++ b/challenge-306/roger-bell-west/rust/ch-2.rs
@@ -0,0 +1,30 @@
+#! /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!(lastelement(vec![3, 8, 5, 2, 9, 2]), 1);
+}
+
+#[test]
+fn test_ex2() {
+    assert_eq!(lastelement(vec![3, 2, 5]), 0);
+}
+
+fn lastelement(a: Vec<u32>) -> u32 {
+    let mut b = a.clone();
+    loop {
+        b.sort();
+        let f = b.pop().unwrap();
+        let s = b.pop().unwrap();
+        if f > s {
+            b.push(f - s);
+        }
+        if b.len() == 0 {
+            return 0;
+        }
+        if b.len() == 1 {
+            return b[0];
+        }
+    }
+}
diff --git a/challenge-306/roger-bell-west/scala/ch-1.scala b/challenge-306/roger-bell-west/scala/ch-1.scala
new file mode 100644
index 0000000000..ac444ca47b
--- /dev/null
+++ b/challenge-306/roger-bell-west/scala/ch-1.scala
@@ -0,0 +1,29 @@
+
+object Oddsum {
+  def oddsum(a: List[Int]): Int = {
+    var out = a.sum
+    var l = 3
+    while (l <= a.size) {
+      for (s <- a.sliding(l)) {
+        out += s.sum
+      }
+      l += 2
+    }
+    out
+  }
+  def main(args: Array[String]) {
+    if (oddsum(List(2, 5, 3, 6, 4)) == 77) {
+      print("Pass")
+    } else {
+      print("Fail")
+    }
+    print(" ")
+    if (oddsum(List(1, 3)) == 4) {
+      print("Pass")
+    } else {
+      print("Fail")
+    }
+    println("")
+
+  }
+}
diff --git a/challenge-306/roger-bell-west/scala/ch-2.scala b/challenge-306/roger-bell-west/scala/ch-2.scala
new file mode 100644
index 0000000000..674d87facb
--- /dev/null
+++ b/challenge-306/roger-bell-west/scala/ch-2.scala
@@ -0,0 +1,42 @@
+import scala.collection.mutable.ListBuffer
+
+object Lastelement {
+  def lastelement(a: List[Int]): Int = {
+    var b = a.to[ListBuffer]
+    var ct = true
+    var ex = -1
+    while (ct) {
+      b = b.sortWith(_ < _)
+      val f = b.last
+      b = b.dropRight(1)
+      val s = b.last
+      b = b.dropRight(1)
+      if (f > s) {
+        b += (f - s)
+      }
+      if (b.size == 0) {
+        ct = false
+        ex = 0
+      }
+      if (b.size == 1) {
+        ct = false
+        ex = b(0)
+      }
+    }
+    ex
+  }
+  def main(args: Array[String]) {
+    if (lastelement(List(3, 8, 5, 2, 9, 2)) == 1) {
+      print("Pass")
+    } else {
+      print("Fail")
+    }
+    print(" ")
+    if (lastelement(List(3, 2, 5)) == 0) {
+      print("Pass")
+    } else {
+      print("Fail")
+    }
+    println("")
+  }
+}
diff --git a/challenge-306/roger-bell-west/tests.json b/challenge-306/roger-bell-west/tests.json
new file mode 100644
index 0000000000..65f1dfc651
--- /dev/null
+++ b/challenge-306/roger-bell-west/tests.json
@@ -0,0 +1,24 @@
+{
+    "ch-1" : [
+        {
+            "function" : "oddsum",
+            "arguments" : [ 2, 5, 3, 6, 4 ],
+            "result" : 77
+        },
+        {
+            "arguments" : [ 1, 3 ],
+            "result" : 4
+        }
+    ],
+    "ch-2" : [
+        {
+            "function" : "lastelement",
+            "arguments" : [ 3, 8, 5, 2, 9, 2 ],
+            "result" : 1
+        },
+        {
+            "arguments" : [ 3, 2, 5 ],
+            "result" : 0
+        }
+    ]
+}