Solutions for challenge #191

18 files changed, 901 insertions, 0 deletions

diff --git a/challenge-191/roger-bell-west/javascript/ch-1.js b/challenge-191/roger-bell-west/javascript/ch-1.js
new file mode 100755
index 0000000000..7daf99853d
--- /dev/null
+++ b/challenge-191/roger-bell-west/javascript/ch-1.js
@@ -0,0 +1,36 @@
+#! /usr/bin/node
+
+"use strict"
+
+function twicelargest(l0) {
+    let l = [...l0];
+    l.sort(function(a,b) {
+        return b-a;
+    });
+    return l[0] >= l[1] * 2;
+}
+
+if (!twicelargest([1, 2, 3, 4])) {
+    process.stdout.write("Pass");
+} else {
+    process.stdout.write("FAIL");
+}
+process.stdout.write(" ");
+if (twicelargest([1, 2, 0, 5])) {
+    process.stdout.write("Pass");
+} else {
+    process.stdout.write("FAIL");
+}
+process.stdout.write(" ");
+if (twicelargest([2, 6, 3, 1])) {
+    process.stdout.write("Pass");
+} else {
+    process.stdout.write("FAIL");
+}
+process.stdout.write(" ");
+if (!twicelargest([4, 5, 2, 3])) {
+    process.stdout.write("Pass");
+} else {
+    process.stdout.write("FAIL");
+}
+process.stdout.write("\n");
diff --git a/challenge-191/roger-bell-west/javascript/ch-2.js b/challenge-191/roger-bell-west/javascript/ch-2.js
new file mode 100755
index 0000000000..424b4641d5
--- /dev/null
+++ b/challenge-191/roger-bell-west/javascript/ch-2.js
@@ -0,0 +1,62 @@
+#! /usr/bin/node
+
+"use strict"
+
+function cutelist(n) {
+    let tab = [[false]];
+    let t = [];
+    for (let x = 1; x <= n; x++) {
+        tab.push(new Array(n+1).fill(false));
+        t.push(x);
+    }
+    for (let x = 1; x <= n; x++) {
+        for (let y = 1; y <= x; y++) {
+            if (x % y != 0 && y % x != 0) {
+                tab[x][y] = true;
+                tab[y][x] = true;
+            }
+        }
+    }
+    let count = 0;
+    let stackl = [[]];
+    let stackc = [t];
+    while (stackl.length != 0) {
+        let l = stackl.pop();
+        let c = stackc.pop();
+        if (c.length == 0 && l.length == n)  {
+            count++;
+        } else {
+            let place = l.length + 1;
+            for (let candidate of c) {
+                if (!tab[place][candidate]) {
+                    let q = Array.from(l);
+                    q.push(candidate);
+                    stackl.push(q);
+                    stackc.push(Array.from(c.filter(i => i != candidate)));
+                }
+            }
+        }
+    }
+    return count;
+}
+
+if (cutelist(2) == 2) {
+    process.stdout.write("Pass");
+} else {
+    process.stdout.write("FAIL");
+}
+process.stdout.write(" ");
+
+if (cutelist(10) == 700) {
+    process.stdout.write("Pass");
+} else {
+    process.stdout.write("FAIL");
+}
+process.stdout.write(" ");
+
+if (cutelist(15) == 24679) {
+    process.stdout.write("Pass");
+} else {
+    process.stdout.write("FAIL");
+}
+process.stdout.write("\n");
diff --git a/challenge-191/roger-bell-west/kotlin/ch-1.kt b/challenge-191/roger-bell-west/kotlin/ch-1.kt
new file mode 100644
index 0000000000..a5b535b011
--- /dev/null
+++ b/challenge-191/roger-bell-west/kotlin/ch-1.kt
@@ -0,0 +1,32 @@
+fun twicelargest(l0: List<Int>): Boolean {
+    var l = ArrayList(l0)
+    l.sort()
+    return l.last() >= 2*l[l.size - 2]
+}
+
+fun main() {
+    if (!twicelargest(listOf(1, 2, 3, 4))) {
+        print("Pass")
+    } else {
+        print("FAIL")
+    }
+    print(" ")   
+    if (twicelargest(listOf(1, 2, 0, 5))) {
+        print("Pass")
+    } else {
+        print("FAIL")
+    }
+    print(" ")   
+    if (twicelargest(listOf(2, 6, 3, 1))) {
+        print("Pass")
+    } else {
+        print("FAIL")
+    }
+    print(" ")   
+    if (!twicelargest(listOf(4, 5, 2, 3))) {
+        print("Pass")
+    } else {
+        print("FAIL")
+    }
+    println("")
+}
diff --git a/challenge-191/roger-bell-west/kotlin/ch-2.kt b/challenge-191/roger-bell-west/kotlin/ch-2.kt
new file mode 100644
index 0000000000..9c445a2027
--- /dev/null
+++ b/challenge-191/roger-bell-west/kotlin/ch-2.kt
@@ -0,0 +1,65 @@
+fun cutelist(n: Int): Int {
+    var tab = ArrayList<ArrayList<Boolean>>()
+    tab.add(arrayListOf(false))
+    for (x in 1..n) {
+        var row = ArrayList<Boolean>()
+        for (y in 1..n+1) {
+            row.add(false)
+        }
+        tab.add(row)
+    }
+    for (x in 1..n) {
+        for (y in 1..x) {
+            if (x % y != 0 && y % x != 0) {
+                tab[x][y] = true
+                tab[y][x] = true
+            }
+        }
+    }
+    var count = 0
+    var stackl = ArrayList<ArrayList<Int>>()
+    stackl.add(arrayListOf())
+    var stackc = ArrayList<ArrayList<Int>>()
+    stackc.add(ArrayList((1..n).toList()))
+    while (stackl.size > 0) {
+        val l = stackl.last()
+        stackl = ArrayList(stackl.dropLast(1))
+        val c = stackc.last()
+        stackc = ArrayList(stackc.dropLast(1))
+        if (c.size == 0 && l.size == n) {
+            count += 1
+        } else {
+            val place = l.size + 1
+            for (candidate in c) {
+                if (!tab[place][candidate]) {
+                    var q = ArrayList(l)
+                    q.add(candidate)
+                    stackl.add(q)
+                    stackc.add(ArrayList(c.filter{it != candidate}))
+                }
+            }
+        }
+    }
+    return count
+}
+
+fun main() {
+    if (cutelist(2) == 2) {
+        print("Pass")
+    } else {
+        print("FAIL")
+    }
+    print(" ")
+    if (cutelist(10) == 700) {
+        print("Pass")
+    } else {
+        print("FAIL")
+    }
+    print(" ")
+    if (cutelist(15) == 24679) {
+        print("Pass")
+    } else {
+        print("FAIL")
+    }
+    println("")
+}
diff --git a/challenge-191/roger-bell-west/lua/ch-1.lua b/challenge-191/roger-bell-west/lua/ch-1.lua
new file mode 100755
index 0000000000..67a03fccb7
--- /dev/null
+++ b/challenge-191/roger-bell-west/lua/ch-1.lua
@@ -0,0 +1,35 @@
+#! /usr/bin/lua
+
+function twicelargest(l0)
+   local l = l0
+   table.sort(l)
+   return l[#l] >= 2 * l[#l-1]
+end
+
+if not twicelargest({1, 2, 3, 4}) then
+   io.write("Pass")
+else
+   io.write("FAIL")
+end
+io.write(" ")
+
+if twicelargest({1, 2, 0, 5}) then
+   io.write("Pass")
+else
+   io.write("FAIL")
+end
+io.write(" ")
+
+if twicelargest({2, 6, 3, 1}) then
+   io.write("Pass")
+else
+   io.write("FAIL")
+end
+io.write(" ")
+
+if not twicelargest({4, 5, 2, 3}) then
+   io.write("Pass")
+else
+   io.write("FAIL")
+end
+print("")
diff --git a/challenge-191/roger-bell-west/lua/ch-2.lua b/challenge-191/roger-bell-west/lua/ch-2.lua
new file mode 100755
index 0000000000..f05338a714
--- /dev/null
+++ b/challenge-191/roger-bell-west/lua/ch-2.lua
@@ -0,0 +1,73 @@
+#! /usr/bin/lua
+
+function cutelist(n)
+   local tab = {}
+   local tmp = {}
+   for x = 1,n do
+      local row = {}
+      for y = 1,n do
+         table.insert(row, false)
+      end
+      table.insert(tab, row)
+      table.insert(tmp, x)
+   end
+   for x = 1,n do
+      for y = 1,x do
+         if x % y ~= 0 and y % x ~= 0 then
+            tab[x][y] = true
+            tab[y][x] = true
+         end
+      end
+   end
+   local count = 0
+   local stackl = {{}}
+   local stackc = {tmp}
+   while #stackl > 0 do
+      local l = table.remove(stackl)
+      local c = table.remove(stackc)
+      if #c == 0 and #l == n then
+         count = count + 1
+      else
+         local place = #l + 1
+         for i, candidate in ipairs(c) do
+            if not tab[place][candidate] then
+               local ql = {}
+               for j, qx in ipairs(l) do
+                  table.insert(ql, qx)
+               end
+               table.insert(ql, candidate)
+               table.insert(stackl, ql)
+               local qc = {}
+               for j, qx in ipairs(c) do
+                  if qx ~= candidate then
+                     table.insert(qc, qx)
+                  end
+               end
+               table.insert(stackc, qc)
+            end
+         end
+      end
+   end
+   return count
+end
+
+if cutelist(2) == 2 then
+   io.write("Pass")
+else
+   io.write("FAIL")
+end
+io.write(" ")
+
+if cutelist(10) == 700 then
+   io.write("Pass")
+else
+   io.write("FAIL")
+end
+io.write(" ")
+
+if cutelist(15) == 24679 then
+   io.write("Pass")
+else
+   io.write("FAIL")
+end
+print("")
diff --git a/challenge-191/roger-bell-west/perl/ch-1.pl b/challenge-191/roger-bell-west/perl/ch-1.pl
new file mode 100755
index 0000000000..5a46a22aac
--- /dev/null
+++ b/challenge-191/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 => 4;
+
+is(twicelargest(1, 2, 3, 4), 0, 'example 1');
+is(twicelargest(1, 2, 0, 5), 1, 'example 2');
+is(twicelargest(2, 6, 3, 1), 1, 'example 3');
+is(twicelargest(4, 5, 2, 3), 0, 'example 4');
+
+sub twicelargest(@l0) {
+  my @l = sort @l0;
+  return ($l[-1] >= 2*$l[-2])?1:0;
+}
diff --git a/challenge-191/roger-bell-west/perl/ch-2.pl b/challenge-191/roger-bell-west/perl/ch-2.pl
new file mode 100755
index 0000000000..e2cf99800a
--- /dev/null
+++ b/challenge-191/roger-bell-west/perl/ch-2.pl
@@ -0,0 +1,44 @@
+#! /usr/bin/perl
+
+use strict;
+use warnings;
+use experimental 'signatures';
+
+use Test::More tests => 3;
+
+is(cutelist(2), 2, 'example 1');
+is(cutelist(10), 700, 'example 2');
+is(cutelist(15), 24679, 'example 3');
+
+sub cutelist($n) {
+  my @tab = ([]);
+  foreach (1..$n) {
+    push @tab,[(0) x ($n+1)];
+  }
+  foreach my $x (1..$n) {
+    foreach my $y (1..$x) {
+      if ($x % $y != 0 && $y % $x != 0) {
+        $tab[$x][$y] = $tab[$y][$x] = 1;
+      }
+    }
+  }
+  my $count = 0;
+  my @stackl = ([]);
+  my @stackc = ([1..$n]);
+  while (@stackl) {
+    my $l = pop @stackl;
+    my $c = pop @stackc;
+    if (scalar @{$c} == 0 && scalar @{$l} == $n) {
+      $count++;
+    } else {
+      my $place = scalar @{$l} + 1;
+      foreach my $candidate (@{$c}) {
+        unless ($tab[$place][$candidate]) {
+          push @stackl,[@{$l},$candidate];
+          push @stackc,[grep {$_ != $candidate} @{$c}];
+        }
+      }
+    }
+  }
+  return $count;
+}
diff --git a/challenge-191/roger-bell-west/postscript/ch-1.ps b/challenge-191/roger-bell-west/postscript/ch-1.ps
new file mode 100644
index 0000000000..fd0cebc81c
--- /dev/null
+++ b/challenge-191/roger-bell-west/postscript/ch-1.ps
@@ -0,0 +1,121 @@
+%!PS
+
+% begin included library code
+% see https://github.com/Firedrake/postscript-libraries/
+/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.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
+
+/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
+
+/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 ge {
+                exit
+            } if
+        } loop
+        {
+            /j j 1 sub def
+            arr j get pivot le {
+                exit
+            } if
+        } loop
+        i j ge {
+            j
+            exit
+        } if
+        i j quicksort.swap
+    } 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
+
+/quicksort { % [ a c b ] -> [ a b c ]
+    1 dict begin
+    /arr exch def
+    arr length 0 gt {
+        0 arr length 1 sub quicksort.main
+    } if
+    arr
+    end
+} bind def
+
+
+% end included library code
+
+/twicelargest {
+    1 dict begin
+    quicksort /l exch def
+    l l length 1 sub get l l length 2 sub get 2 mul ge
+    end
+} bind def
+
+(twicelargest) test.start
+[ 1 2 3 4 ] twicelargest not test
+[ 1 2 0 5 ] twicelargest test
+[ 2 6 3 1 ] twicelargest test
+[ 4 5 2 3 ] twicelargest not test
+test.end
diff --git a/challenge-191/roger-bell-west/postscript/ch-2.ps b/challenge-191/roger-bell-west/postscript/ch-2.ps
new file mode 100644
index 0000000000..3f7bc021c2
--- /dev/null
+++ b/challenge-191/roger-bell-west/postscript/ch-2.ps
@@ -0,0 +1,116 @@
+%!PS
+
+% begin included library code
+% see https://github.com/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
+
+/apop.right { % [a b c] -> [a b] c
+    [ exch aload length 1 add 1 roll ] exch
+} 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
+
+/filter { % array proc(bool) -> array
+    1 dict begin
+    /p exch def
+    [ exch
+      {
+          dup p not
+          {
+              pop
+          } if
+      } forall
+    ]
+    end
+} bind def
+
+/apush.right { % [a b] c -> [a b c]
+    exch
+    [ exch aload length 2 add -1 roll ]
+} bind def
+
+
+% end included library code
+
+/cutelist {
+    11 dict begin
+    /n exch def
+    /tab [
+        [ ]
+        n {
+            [
+                false
+                n {
+                    dup
+                } repeat
+            ]
+        } repeat
+    ] def
+    1 1 n {
+        /x exch def
+        1 1 x {
+            /y exch def
+            x y mod 0 ne y x mod 0 ne and {
+                tab x get y true put
+                tab y get x true put
+            } if
+        } for
+    } for
+    /ct 0 def
+    /stackl [ [ ] ] def
+    /stackc [ [ 1 1 n {} for ] ] def
+    {
+        stackl length 0 eq {
+            exit
+        } if
+        stackl apop.right /l exch def /stackl exch def
+        stackc apop.right /c exch def /stackc exch def
+        c length 0 eq l length n eq and {
+            /ct ct 1 add def
+        } {
+            /place l length 1 add def
+            c {
+                /candidate exch def
+                tab place get candidate get not {
+                    /stackl stackl [ l aload pop candidate ] apush.right def
+                    /stackc stackc [ c { candidate ne } filter aload pop ] apush.right def
+                } if
+            } forall
+        } ifelse
+    } loop
+    ct
+    end
+} bind def
+
+(cutelist) test.start
+2 cutelist 2 eq test
+10 cutelist 700 eq test
+15 cutelist 24679 eq test
+test.end
diff --git a/challenge-191/roger-bell-west/python/ch-1.py b/challenge-191/roger-bell-west/python/ch-1.py
new file mode 100755
index 0000000000..0b0c0c6ba1
--- /dev/null
+++ b/challenge-191/roger-bell-west/python/ch-1.py
@@ -0,0 +1,25 @@
+#! /usr/bin/python3
+
+import unittest
+import re
+
+def twicelargest(l0):
+  l = l0
+  l.sort()
+  return l[-1] >= (2 * l[-2])
+
+class TestTwicelargest(unittest.TestCase):
+
+  def test_ex1(self):
+    self.assertEqual(twicelargest([1, 2, 3, 4]), False, "example 1")
+
+  def test_ex2(self):
+    self.assertEqual(twicelargest([1, 2, 0, 5]), True, "example 2")
+
+  def test_ex3(self):
+    self.assertEqual(twicelargest([2, 6, 3, 1]), True, "example 3")
+
+  def test_ex4(self):
+    self.assertEqual(twicelargest([4, 5, 2, 3]), False, "example 4")
+
+unittest.main()
diff --git a/challenge-191/roger-bell-west/python/ch-2.py b/challenge-191/roger-bell-west/python/ch-2.py
new file mode 100755
index 0000000000..a06335557f
--- /dev/null
+++ b/challenge-191/roger-bell-west/python/ch-2.py
@@ -0,0 +1,43 @@
+#! /usr/bin/python3
+
+import unittest
+
+def cutelist(n):
+  tab = [[False]]
+  for x in range(1, n+1):
+    tab.append([False] * (n+1))
+  for x in range(1, n+1):
+    for y in range(1, x+1):
+      if x % y != 0 and y % x != 0:
+        tab[x][y] = True
+        tab[y][x] = True
+  count = 0
+  stackl = [[]]
+  stackc = [[x for x in range(1,n+1)]]
+  while len(stackl) > 0:
+    l = stackl.pop()
+    c = stackc.pop()
+    if len(c) == 0 and len(l) == n:
+      count += 1
+    else:
+      place = len(l) + 1
+      for candidate in c:
+        if not tab[place][candidate]:
+          q = l.copy()
+          q.append(candidate)
+          stackl.append(q)
+          stackc.append([i for i in c if i != candidate])
+  return count
+
+class TestCutelist(unittest.TestCase):
+
+  def test_ex1(self):
+    self.assertEqual(cutelist(2), 2, 'example 1')
+
+  def test_ex2(self):
+    self.assertEqual(cutelist(10), 700, 'example 2')
+
+  def test_ex3(self):
+    self.assertEqual(cutelist(15), 24679, 'example 3')
+
+unittest.main()
diff --git a/challenge-191/roger-bell-west/raku/ch-1.p6 b/challenge-191/roger-bell-west/raku/ch-1.p6
new file mode 100755
index 0000000000..cd79a8e17d
--- /dev/null
+++ b/challenge-191/roger-bell-west/raku/ch-1.p6
@@ -0,0 +1,15 @@
+#! /usr/bin/perl6
+
+use Test;
+
+plan 4;
+
+is(twicelargest([1, 2, 3, 4]), False, 'example 1');
+is(twicelargest([1, 2, 0, 5]), True, 'example 2');
+is(twicelargest([2, 6, 3, 1]), True, 'example 3');
+is(twicelargest([4, 5, 2, 3]), False, 'example 4');
+
+sub twicelargest(@l0) {
+    my @l = @l0.sort;
+    return @l[*-1] >= 2*@l[*-2];
+}
diff --git a/challenge-191/roger-bell-west/raku/ch-2.p6 b/challenge-191/roger-bell-west/raku/ch-2.p6
new file mode 100755
index 0000000000..c8588cf1f8
--- /dev/null
+++ b/challenge-191/roger-bell-west/raku/ch-2.p6
@@ -0,0 +1,45 @@
+#! /usr/bin/perl6
+
+use Test;
+
+plan 3;
+
+is(cutelist(2), 2, 'example 1');
+is(cutelist(10), 700, 'example 2');
+is(cutelist(15), 24679, 'example 3');
+
+sub cutelist($n) {
+    my @tab = ([]);
+    for (1..$n) {
+        @tab.push([False xx ($n+1)]);
+    }
+    for (1..$n) -> $x {
+        for (1..$x) -> $y {
+            if ($x % $y != 0 && $y % $x != 0) {
+                @tab[$x][$y] = @tab[$y][$x] = True;
+            }
+        }
+    }
+    my $count = 0;
+    my @stackl = [[],];
+    my @stackc = [[1..$n],];
+    while (@stackl.elems > 0) {
+        my @l = @stackl.pop.flat;
+        my @c = @stackc.pop.flat;
+        if (@c.elems == 0 && @l.elems == $n) {
+            $count++;
+        } else {
+            my $place = @l.elems + 1;
+            for @c -> $candidate {
+                unless (@tab[$place][$candidate]) {
+                    my @q = @l.clone;
+                    @q.push($candidate);
+                    @stackl.push(@q);
+                    my @qc = @c.grep({$_ != $candidate});
+                    @stackc.push(@qc);
+                }
+            }
+        }
+    }
+    return $count;
+}
diff --git a/challenge-191/roger-bell-west/ruby/ch-1.rb b/challenge-191/roger-bell-west/ruby/ch-1.rb
new file mode 100755
index 0000000000..9aabe23c24
--- /dev/null
+++ b/challenge-191/roger-bell-west/ruby/ch-1.rb
@@ -0,0 +1,27 @@
+#! /usr/bin/ruby
+
+require 'test/unit'
+
+def twicelargest(l0)
+  l = l0.sort
+  return l[-1] >= (2 * l[-2])
+end
+
+class TestDivisiblepairs < Test::Unit::TestCase
+
+  def test_ex1
+    assert_equal(false, twicelargest([1, 2, 3, 4]))
+  end
+
+  def test_ex2
+    assert_equal(true, twicelargest([1, 2, 0, 5]))
+  end
+
+  def test_ex3
+    assert_equal(true, twicelargest([2, 6, 3, 1]))
+  end
+
+  def test_ex4
+    assert_equal(false, twicelargest([4, 5, 2, 3]))
+  end
+end
diff --git a/challenge-191/roger-bell-west/ruby/ch-2.rb b/challenge-191/roger-bell-west/ruby/ch-2.rb
new file mode 100755
index 0000000000..735ac64d30
--- /dev/null
+++ b/challenge-191/roger-bell-west/ruby/ch-2.rb
@@ -0,0 +1,56 @@
+#! /usr/bin/ruby
+
+require 'test/unit'
+
+require 'set'
+
+def cutelist(n)
+  tab = [[false]]
+  1.upto(n) do
+    tab.push([false] * (n+1))
+  end
+  1.upto(n) do |x|
+    1.upto(x) do |y|
+      if x % y != 0 && y % x != 0 then
+        tab[x][y] = true
+        tab[y][x] = true
+      end
+    end
+  end
+  count = 0
+  stackl = [[]]
+  stackc = [(1..n).to_a]
+  while stackl.length > 0 do
+    l = stackl.pop
+    c = stackc.pop
+    if c.length == 0 && l.length == n then
+      count += 1
+    else
+      place = l.length + 1
+      c.each do |candidate|
+        if !tab[place][candidate] then
+          q = l[0..-1]
+          q.push(candidate)
+          stackl.push(q)
+          stackc.push(c.reject {|i| i == candidate})
+        end
+      end
+    end
+  end
+  return count
+end
+
+class TestCutelist < Test::Unit::TestCase
+
+  def test_ex1
+    assert_equal(2, cutelist(2));
+  end
+
+  def test_ex2
+    assert_equal(700, cutelist(10));
+  end
+
+  def test_ex3
+    assert_equal(24679, cutelist(15));
+  end
+end
diff --git a/challenge-191/roger-bell-west/rust/ch-1.rs b/challenge-191/roger-bell-west/rust/ch-1.rs
new file mode 100755
index 0000000000..12cd0c5e4d
--- /dev/null
+++ b/challenge-191/roger-bell-west/rust/ch-1.rs
@@ -0,0 +1,29 @@
+#! /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!(twicelargest(vec![1, 2, 3, 4]), false);
+}
+
+#[test]
+fn test_ex2() {
+    assert_eq!(twicelargest(vec![1, 2, 0, 5]), true);
+}
+
+#[test]
+fn test_ex3() {
+    assert_eq!(twicelargest(vec![2, 6, 3, 1]), true);
+}
+
+#[test]
+fn test_ex4() {
+    assert_eq!(twicelargest(vec![4, 5, 2, 3]), false);
+}
+
+fn twicelargest(l0: Vec<u64>) -> bool {
+    let mut l = l0.clone();
+    l.sort();
+    l.reverse();
+    l[0] >= 2 * l[1]
+}
diff --git a/challenge-191/roger-bell-west/rust/ch-2.rs b/challenge-191/roger-bell-west/rust/ch-2.rs
new file mode 100755
index 0000000000..25875b2184
--- /dev/null
+++ b/challenge-191/roger-bell-west/rust/ch-2.rs
@@ -0,0 +1,60 @@
+#! /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!(cutelist(2), 2);
+}
+
+#[test]
+fn test_ex2() {
+    assert_eq!(cutelist(10), 700);
+}
+
+#[test]
+fn test_ex3() {
+    assert_eq!(cutelist(15), 24679);
+}
+
+fn cutelist(n: usize) -> usize {
+    let mut tab: Vec<Vec<bool>> = Vec::new();
+    tab.push(Vec::new());
+    for _ in 1..=n {
+        tab.push(vec![false; n + 1]);
+    }
+    for x in 1..=n {
+        for y in 1..=x {
+            if x % y != 0 && y % x != 0 {
+                tab[x][y] = true;
+                tab[y][x] = true;
+            }
+        }
+    }
+    let mut count = 0;
+    let mut stackl: Vec<Vec<usize>> = vec![Vec::new()];
+    let mut stackc: Vec<Vec<usize>> = Vec::new();
+    stackc.push((1..=n).collect::<Vec<usize>>());
+    while stackl.len() > 0 {
+        let l = stackl.pop().unwrap();
+        let c = stackc.pop().unwrap();
+        if c.len() == 0 && l.len() == n {
+            count += 1;
+        } else {
+            let place = l.len() + 1;
+            for &candidate in &c {
+                if !tab[place][candidate] {
+                    let mut q = l.clone();
+                    q.push(candidate);
+                    stackl.push(q);
+                    stackc.push(
+                        c.iter()
+                            .filter(|i| **i != candidate)
+                            .map(|i| *i)
+                            .collect::<Vec<usize>>(),
+                    );
+                }
+            }
+        }
+    }
+    count
+}