Question

Create an alternative implementation of the numUnique method from the previous problem that has a better worst-case time efficiency than the original method. Like the original method, you may assume that arr is not null, and you may also assume that it has at least one element. Make your implementation as efficient as possible.

Answer 1

To create an alternative implementation of the numUnique method with a better worst-case time efficiency, we can use a HashSet instead of an ArrayList. This implementation has a better worst-case time efficiency of O(n), where n is the number of elements in the array.

Step-by-step explanation:

Alternative Implementation with Better Worst-Case Time Efficiency

To create an alternative implementation of the numUnique method with a better worst-case time efficiency, we can use a HashSet instead of an ArrayList. A HashSet is a data structure that stores unique elements, allowing us to easily count the number of unique elements in an array. Here's an example implementation:

import java.util.HashSet;

public static int numUnique(int[] arr) {
HashSet set = new HashSet<>();
for (int num : arr) {
set.add(num);
}
return set.size();
}

This implementation has a better worst-case time efficiency of O(n), where n is the number of elements in the array. This is because HashSet operations such as add and size have an average time complexity of O(1) for a single element, resulting in a more efficient solution.