Nitpick: O(m+n) where m>n is just O(m). The point is, the operation is of linear order in the larger number of items.
Also, this is computationally O(1), but the original post asks for memory usage, not computation. I'm not a high enough level monk to know what the memory usage of arrays vs. hashes is, but I would hazard a guess that unless you're using an embedded environment or something else with very little available memory, that at 10k items you don't need to care too much about that.

Ben

---

---

• 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 How to display code and escape characters are good places to start.