Welcome to our focused exploration of Kotlin's HashSet and its remarkable applications in solving algorithmic challenges. In this lesson, "Mastering Unique Elements and Anagram Detection with Kotlin 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.

A basic approach would involve counting occurrences of each word by scanning the entire array for each word, resulting in an O(n^2) time complexity.

Here is the naive approach in Kotlin:

In this naive implementation, we iterate backwards through the array and for each word, we scan the entire array to count its occurrences. The first word we encounter with a count of 1 is our last unique word.