Count Distinct Elements

/*
 * Problem : Process an array.
 * Input   : n, then n integers.
 * Output  : The number of different values.
 * Approach: Use a set.
 * Time    : O(n)
 * Space   : O(n)
 * Java    : 8 or newer.
 */
import java.util.Scanner;

public class Main {
    // This method solves the task. It receives the input and returns the answer.
    static int solve(int[] a) {
        // Step 1: A HashSet keeps only different values.
        java.util.Set<Integer> unique = new java.util.HashSet<>();
        for (int value : a) {
            unique.add(value);
        }

        // Step 2: The size of the set is the answer.
        return unique.size();
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int size = scanner.nextInt();
        int[] a = new int[size];
        for (int i = 0; i < size; i++) {
            a[i] = scanner.nextInt();
        }
        System.out.println(solve(a));
    }
}