Time for an 2014 update…

Task/Topswops/Erlang/topswops.erl

@@ -0,0 +1,21 @@
+-module( topswops ).
+
+-export( [get_1_first/1, swap/1, task/0] ).
+
+get_1_first( [1 | _T] ) -> 0;
+get_1_first( List ) -> 1 + get_1_first( swap(List) ).
+
+swap( [N | _T]=List ) ->
+	{Swaps, Remains} = lists:split( N, List ),
+	lists:reverse( Swaps ) ++ Remains.
+	
+task() ->
+	Permutations = [{X, permute:permute(lists:seq(1, X))} || X <- lists:seq(1, 10)],
+	Swops = [{N, get_1_first_many(N_permutations)} || {N, N_permutations} <- Permutations],
+	Topswops = [{N, lists:max(N_swops)} || {N, N_swops} <- Swops],
+	io:fwrite( "N	topswaps~n" ),
+	[io:fwrite("~p	~p~n", [N, Max]) || {N, Max} <- Topswops].
+
+
+
+get_1_first_many( N_permutations ) -> [get_1_first(X) ||  X <- N_permutations].

Task/Topswops/PL-I/topswops.pli

@@ -0,0 +1,32 @@
+(subscriptrange):
+topswap: procedure options (main); /* 12 November 2013 */
+   declare cards(*) fixed (2) controlled, t fixed (2);
+   declare dealt(*) bit(1) controlled;
+   declare (count, i, m, n, c1, c2) fixed binary;
+   declare random builtin;
+
+   do n = 1 to 10;
+      allocate cards(n), dealt(n);
+      /* Take the n cards, in order ... */
+      do i = 1 to n; cards(i) = i; end;
+      /* ... and shuffle them. */
+      do i = 1 to n;
+         c1 = random*n+1; c2 = random*n+1;
+         t = cards(c1); cards(c1) = cards(c2); cards(c2) = t;
+      end;
+      /* If '1' is the first card, game is trivial; swap it with another. */
+      if cards(1) = 1 & n > 1 then
+         do; t = cards(1); cards(1) = cards(2); cards(2) = t; end;
+
+      count = 0;
+      do until (cards(1) = 1);
+         /* take the value of the first card, M, and reverse the first M cards. */
+         m = cards(1);
+         do i = 1 to m/2;
+            t = cards(i); cards(i) = cards(m-i+1); cards(m-i+1) = t;
+         end;
+         count = count + 1;
+      end;
+      put skip edit (n, ':', count) (f(2), a, f(4));
+   end;
+end topswap;

Task/Topswops/Perl/topswops.pl

@@ -0,0 +1,35 @@
+sub next_swop {
+  my( $max, $level, $p, $d ) = @_;
+  my $swopped = 0;
+  for( 2..@$p ){ # find possibilities
+    my @now = @$p;
+    if( $_ == $now[$_-1] ) {
+      splice @now, 0, 0, reverse splice @now, 0, $_;
+      $swopped = 1;
+      next_swop( $max, $level+1, \@now, [ @$d ] );
+    }
+  }
+  for( 1..@$d ) { # create possibilities
+    my @now = @$p;
+    my $next = shift @$d;
+    if( not $now[$next-1] ) {
+      $now[$next-1] = $next;
+      splice @now, 0, 0, reverse splice @now, 0, $next;
+      $swopped = 1;
+      next_swop( $max, $level+1, \@now, [ @$d ] );
+    }
+    push @$d, $next;
+  }
+  $$max = $level if !$swopped and $level > $$max;
+}
+
+sub topswops {
+  my $n = shift;
+  my @d = 2..$n;
+  my @p = ( 1, (0) x ($n-1) );
+  my $max = 0;
+  next_swop( \$max, 0, \@p, \@d );
+  return $max;
+}
+
+printf "Maximum swops for %2d cards: %2d\n", $_, topswops $_ for 1..10;