# 929.Unique Email Addresses

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 name** part 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?&#x20;

**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.

```java
class Solution {
    public int numUniqueEmails(String[] emails) {
        if(emails == null || emails.length == 0) return 0;
        
        Set<String> set = new HashSet<>();
        
        for(String email : emails){
            String[] strArr = email.split("@");
            StringBuilder sb = new StringBuilder();
            
            for(char c : strArr[0].toCharArray()){
                if(c == '+'){
                  
                    break;
                }
                
                if(c =='.') continue;
                
                sb.append(c);
            }
            
             sb.append("@");
            sb.append(strArr[1]);
            set.add(sb.toString());
        }
        
        return set.size();
    }
}
```
