Beefy Boxes and Bandwidth Generously Provided by pair Networks
Don't ask to ask, just ask

comment on

( #3333=superdoc: print w/replies, xml ) Need Help??

It should be noted that many algorithm's O time can be reduced. For instance, many O(n^2) algorithms can be reduced to O(n log(n)) by finding a way to cut the inner loop short. A famous example is bubblesort:

# O(n^2) for my $i (0..$#a-1) { for (0..$#a-1-$i) { ($a[$_],$a[$_+1]) = ($a[$_+1],$a[$_]) if ($a[$_+1] < $a[$_]); } } # O(n log(n)) for my $i (0..$#a-1) { # looping over already-sorted items is not needed for (0..$#a-1-$i) { ($a[$_],$a[$_+1]) = ($a[$_+1],$a[$_]) if ($a[$_+1] < $a[$_]); } }

O(n) algorithms that involve a search via a loop can sometimes be reduced from O(n) to O(log(n)) by breaking out of the loop once a "result" is found:

# O(n) my $truestatus; foreach my $item (@list) { $truestatus = 1 if (some_condition); } # O(log(n)) my $truestatus; foreach my $item (@list) { # if some_condition is going to be valid for at least one $item in # @list, then the limit of the average runtime will approach # O(log n). if (some_condition) { $truestatus = 1; last } }

Of course, the secret is to know where to apply these optimizations, which is often harder than it seems :)

In reply to Re: An informal introduction to O(N) notation by jryan
in thread An informal introduction to O(N) notation by dws

Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post; it's "PerlMonks-approved HTML":

  • Are you posting in the right place? Check out Where do I post X? to know for sure.
  • Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:
    <code> <a> <b> <big> <blockquote> <br /> <dd> <dl> <dt> <em> <font> <h1> <h2> <h3> <h4> <h5> <h6> <hr /> <i> <li> <nbsp> <ol> <p> <small> <strike> <strong> <sub> <sup> <table> <td> <th> <tr> <tt> <u> <ul>
  • Snippets of code should be wrapped in <code> tags not <pre> tags. In fact, <pre> tags should generally be avoided. If they must be used, extreme care should be taken to ensure that their contents do not have long lines (<70 chars), in order to prevent horizontal scrolling (and possible janitor intervention).
  • Want more info? How to link or or How to display code and escape characters are good places to start.
Log In?

What's my password?
Create A New User
Domain Nodelet?
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others chanting in the Monastery: (5)
As of 2022-09-26 08:52 GMT
Find Nodes?
    Voting Booth?
    I prefer my indexes to start at:

    Results (117 votes). Check out past polls.