Merge branch 'master' of https://github.com/drbaggy/perlweeklychallenge-club

1 files changed, 29 insertions, 19 deletions

diff --git a/challenge-114/james-smith/perl/ch-1.pl b/challenge-114/james-smith/perl/ch-1.pl
index be0c22adc6..8303864dbd 100644
--- a/challenge-114/james-smith/perl/ch-1.pl
+++ b/challenge-114/james-smith/perl/ch-1.pl
@@ -11,16 +11,28 @@ my @tests = ([1,2],[9,11],[99,101],[989,999],[999,1001],[10,11],[11,22],[12,22],
  [111222,112211]);
 #@tests = map { chomp; [split] } <>;
 
-#is( next_palindrome(       $_->[0] ), $_->[1] ) foreach @tests;
-#is( next_palindrome_naive( $_->[0] ), $_->[1] ) foreach @tests;
+is( next_palindrome(       $_->[0] ), $_->[1] ) foreach @tests;
+is( next_palindrome_naive( $_->[0] ), $_->[1] ) foreach @tests;
 
 done_testing();
 
 use Benchmark qw{ cmpthese };
-cmpthese(2000, {
-  slow => sub { next_palindrome_naive($_) for 99699..100400 },
-  fast => sub { next_palindrome($_)       for 99699..100400 },
-});
+my @ranges = (
+  [ 100_000, 1, 101 ],
+  [ 50_000, 950, 1050 ],
+  [ 20_000, 9950, 10050 ],
+  [ 10_000, 99950, 100050 ],
+  [ 5_000, 999950, 1000050 ],
+  [ 1_000, 9999950, 10000050 ],
+  [ 1_000, 99999950, 100000050 ],
+);
+
+foreach my $r (@ranges) {
+  cmpthese($r->[0], {
+    slow => sub { next_palindrome_naive($_) for $r->[1] .. $r->[2] },
+    fast => sub { next_palindrome($_)       for $r->[1] .. $r->[2] },
+  });
+}
 
 sub next_palindrome_naive {
   my ($n) = @_;
@@ -29,8 +41,8 @@ sub next_palindrome_naive {
 }
 
 sub next_palindrome {
-  my $p  = 1 + (my $n = shift);
-  my $x = substr $p, 0, (length $p)>>1; $x||='';
+  my $p  = 1 + shift;
+  my $x = substr $p, 0, (length $p)>>1;
   if( 1 & length $p ) {
     ## Odd length so we have three options...
     ## new number by reversing the first half of the number > $n so OK!
@@ -41,19 +53,17 @@ sub next_palindrome {
     ## then 999.9.999 > 999.9.998 and so we don't get this... so we
     ## are safe with this approach...
     my $y = substr $p, (length$p)>>1, 1;
-    return $x.$y.reverse $x      if $n < $x.$y.reverse $x;
+    return $x.$y.reverse $x      if $p <= $x.$y.reverse $x;
     return $x.($y+1).reverse $x  if $y<9;
-    $x++;
-    return $x.'0'.reverse $x;
-  } else {
-    ## Even no of digits..
-    ## If $n >= $x.reverse $x we incrememnt $x;
-    ## The only time that this could lead to a longer number is when
-    ## $x is 999 and is OK as $x.reverse $x will always be larger than
-    ## $n....
-    $x++ if $n >= $x.reverse $x;
-    return $x.reverse $x;
+    return ++$x.'0'.reverse $x;
   }
+  ## Even no of digits..
+  ## If $n >= $x.reverse $x we incrememnt $x;
+  ## The only time that this could lead to a longer number is when
+  ## $x is 999 and is OK as $x.reverse $x will always be larger than
+  ## $n....
+  return $x.reverse $x  if $p <= $x.reverse $x;
+  return ++$x.reverse $x;
 }