How would you display an array of integers as a set of ranges? (algorithm)

Question

Given an array of integers, what is the simplest way to iterate over it and figure out all the ranges it covers? for example, for an array such as:

$numbers = ar         


        

Answer 1

Here's my Perl solution. Could be cleaner and faster, but it shows how it works:

# Just in case it's not sorted...
my @list = sort { $a <=> $b } ( 1, 3, 4, 5, 6, 8, 11, 12, 14, 15, 16 );

my $range = [ $list[0] ];

for(@list[1 .. $#list]) {
    if($_ == $range->[-1] + 1) {
        push @$range, $_;
    }
    else {
        print $#$range ? $range->[0] . '-' . $range->[-1] : $range->[0], "\n";
        $range = [ $_ ];
    }
}