Algorithm: efficient way to remove duplicate integers from an array

Question

I got this problem from an interview with Microsoft.

Given an array of random integers, write an algorithm in C that removes duplicated numbers an

Answer 1

Insert all the elements in a binary tree the disregards duplicates - O(nlog(n)). Then extract all of them back in the array by doing a traversal - O(n). I am assuming that you don't need order preservation.