Sponsored
Sponsored
In this approach, we'll use a set to store unique email addresses. We'll iterate over each email, split it into local and domain parts, then manipulate the local part by removing any characters after the first '+' and all periods '.' before rejoining with the domain. Finally, we'll add the standardized email to the set. The size of the set gives the count of unique emails.
Time Complexity: O(N * M) where N is the number of emails and M is the maximum length of an email address.
Space Complexity: O(N) due to the storage of unique emails in a set.
1import java.util.HashSet;
2import java.util.Set;
3
4public class UniqueEmail {
5 public int numUniqueEmails(String[] emails) {
6 Set<String> uniqueEmails = new HashSet<>();
7 for (String email : emails) {
8 String[] parts = email.split("@");
9 String local = parts[0];
10 String domain = parts[1];
11 int plusIndex = local.indexOf('+');
12 if (plusIndex != -1) {
13 local = local.substring(0, plusIndex);
14 }
15 local = local.replaceAll(".", "");
16 uniqueEmails.add(local + "@" + domain);
17 }
18 return uniqueEmails.size();
19 }
20}In Java, employ a HashSet to maintain unique email addresses. Divide each email using '@' to get local and domain parts. When '+' is found within the local, truncate it. Eliminate all '.' from the local. Subsequently, concatenate with the domain and incorporate into the set. The number of unique emails equal the set's size.
In this approach, instead of transforming emails directly using a set, we'll utilize arrays to manipulate the email parts. We'll maintain a boolean array for discovered unique emails and an index array to track up to where the email is unique. This efficient tracking helps us determine unique addresses without full storage, but more focused on transformations directly performed within the iteration loop.
Time Complexity: O(N * M), since per email processed once fully.
Space Complexity: O(N), enabling efficient tracking of unique addresses.
Using a Stream in Java for a different methodology of going through emails and converting components directly using boolean switches for '@' and '+' provides a twist compared to default library methods.