import java.util.HashSet; class Solution { public int numUniqueEmails(String[] emails) { HashSet emailSet = new HashSet<>(); for (String email: emails) { String firstSplit[] = email.split("@"); String secondSplit[] = firstSplit[0].replaceAll(".", "").split("[+]"); emailSet.add(secondSplit[0] + firstSplit[1]); } return emailSet.size(); } }