Update ch-2.pl

Use REGEX extraction to find intersections of paths.

1 files changed, 20 insertions, 0 deletions

diff --git a/challenge-012/jaime/perl5/ch-2.pl b/challenge-012/jaime/perl5/ch-2.pl
index 7a4262c7f6..15c1312e46 100644
--- a/challenge-012/jaime/perl5/ch-2.pl
+++ b/challenge-012/jaime/perl5/ch-2.pl
@@ -15,3 +15,23 @@
 #
 # and the path separator is `/`. Your script should return `/a/b` as common
 # directory path.
+
+my $delim = shift; # delimit a path, for example `/`.
+
+my $pelim = ":"; # delimit paths, for example unix uses `:`.
+my @paths = split /$pelim/, shift; # list of paths, for example `/bin:/sbin`.
+
+# at best, the first path is completely common within all paths
+my $common = @paths[0];
+
+PATH: for my $path (@paths) {
+    next PATH if $path =~ /^$common/; # $common at the start of $path.
+    while (($common) = ($common =~ /^(.*)$delim/)) {
+	last if $path =~ /^$common/; # otherwise find intersection of $common and $path.
+    }
+    last PATH unless $common; # stop if a $path is completely unique.
+}
+
+($common) = (@paths[0] =~ /^($delim)/) unless $common; # if given, root is always common
+
+print "$common\n";