Welcome to our focused exploration of C#'s HashSet and its remarkable applications in solving algorithmic challenges. In this lesson, "Mastering Unique Elements and Anagram Detection with C# HashSet," we'll delve into how this efficient data structure can be leveraged to address and solve various types of problems commonly encountered in technical interviews.

Picture this: you're given a vast list of words, and you must identify the final word that stands proudly solitary — the last word that is not repeated. Imagine sorting through a database of unique identifiers and finding one identifier towards the end of the list that is unlike any other.

The straightforward approach would be to examine each word in reverse, comparing it to every other word for uniqueness. This brute-force method would result in poor time complexity, O(n^2), which is less than ideal for large datasets.

Here is the naive approach in C#:

We can utilize two HashSet<string> instances: wordsSet to maintain unique words and to keep track of duplicate words. By the end, we can remove all duplicated words from to achieve our goal. Here is how to use to solve the problem in C#: