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

For example, in[email protected], aliceis the local name, andleetcode.comis the domain name.

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

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

If you add a plus ('+') in thelocal name, everything after the first plus sign will be ignored. This allows certain emails to be filtered, for example [email protected] will be forwarded to [email protected]. (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 ofemails, we send one email to each address in the list. How many different addresses actually receive mails?

Example 1:

Input: ["[email protected]","[email protected]","[email protected]"]
Output: 2
Explanation: "[email protected]" and "[email protected]" actually receive mails

这题也比较直接，目测面试不会出，处理一下local name，然后统计不同email address个数

class Solution {
    public int numUniqueEmails(String[] emails) {
        if(emails == null || emails.length == 0)
            return 0;

        HashSet<String> set = new HashSet<String>();
        for(String email: emails) {
            String processed = process(email);
            if(processed.length() != 0)
                set.add(processed);
        }

        return set.size();
    }

    public String process(String email) {
        if(email == null || email.length() <= 1)
            return "";

        int delimiterIndex = 0;
        while(delimiterIndex != email.length() && email.charAt(delimiterIndex) != '@')
            delimiterIndex++;

        StringBuilder localName = new StringBuilder();
        for(int i = 0; i < delimiterIndex; i++) {
            char c = email.charAt(i);

            if(c == '.') {
                continue;
            } else if(c == '+') {
                break;
            } else {
                localName.append(c);
            }
        }

        return localName.append(email.substring(delimiterIndex)).toString();
    }
}