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#!/usr/bin/env perl
#
# Write a script that finds the common directory path, given a collection of
# paths and directory separator. For example, if the following paths are
# supplied
#
# /a/b/c/d
# /a/b/cd
# /a/b/cc
# /a/b/c/d/e
#
# and the path separator is /. Your script should return /a/b as common
# directory path.
################################################################################
use strict;
use warnings;
sub commonPath {
# Normalize paths (merge multiple "/"s into a single one)
map s|/+|/|g, @_;
# This array stores the common path components so far
my @common = split m|/|, shift, -1;
# Iterate over arguments (paths) and update @common accordingly
foreach my $path (@_) {
my @current = split m|/|, $path, -1;
# Cut @common if longer than the current one
@common = @common[0 .. $#current] if $#current < $#common;
# Cut @common to keep only the matching components
foreach my $i (0 .. $#common) {
if ($common[$i] ne $current[$i]) {
@common = @common[0 .. $i-1];
last;
}
}
}
# Corner case: @common == ('') means root
return @common == 1 && $common[0] eq ''
? "/"
: join "/", @common;
}
# CLI usage
if (@ARGV) {
print commonPath(@ARGV), "\n";
} else {
print "Usage: $0 path1 path2 ...\n";
}
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