#### QUESTION:

Every email consists of a local name and a domain name, separated by the @ sign.

For example, in `alice@leetcode.com`, `alice` is the local name, and `leetcode.com` is the domain name.

Besides lowercase letters, these emails may contain `'.'`s or `'+'`s.

If you add periods (`'.'`) between some characters in the local namepart of an email address, mail sent there will be forwarded to the same address without dots in the local name. For example, `"alice.z@leetcode.com"` and `"alicez@leetcode.com"`forward to the same email address. (Note that this rule does not apply for domain names.)

If you add a plus (`'+'`) in the local name, everything after the first plus sign will be ignored. This allows certain emails to be filtered, for example `m.y+name@email.com` will be forwarded to `my@email.com`. (Again, this rule does not apply for domain names.)

It is possible to use both of these rules at the same time.

Given a list of `emails`, we send one email to each address in the list. How many different addresses actually receive mails?

Example 1:

``````Input: ["test.email+alex@leetcode.com","test.e.mail+bob.cathy@leetcode.com","testemail+david@lee.tcode.com"]
Output: 2
Explanation: "testemail@leetcode.com" and "testemail@lee.tcode.com" actually receive mails
``````

Note:

• `1 <= emails[i].length <= 100`
• `1 <= emails.length <= 100`
• Each `emails[i]` contains exactly one `'@'` character.

#### SOLUTION:

``````class Solution {
public int numUniqueEmails(String[] emails) {
HashSet<String> result = new HashSet<>();
StringBuilder builder = new StringBuilder();
for (String email : emails) {
char[] chars = email.toCharArray();
builder.delete(0, builder.length());
boolean plus = false;
for (int i = 0; i < chars.length; i++) {
char tmp = chars[i];
if (tmp == '.') {
continue;
} else if (tmp == '+') {
plus = true;
} else if (tmp == '@') {
plus = false;
builder.append(chars,i,chars.length-i);
} else {
if (!plus)
builder.append(tmp);
}
}