This is a frequently asked question, the Search window will find the answer for you.

• If order doesn't matter, use the values as keys to a hash, then extract a list of the keys.
• If order does matter, go through the list, copying elements which have not been seen yet. As each element is copied, mark it as seen by setting a hash element.
• go through the original array, checking whether an element has been seen yet, unsplice-ing duplicates.

Good luck with your homework.