UniqueEmailAddresses.cpp

// Source : https://leetcode.com/problems/unique-email-addresses/
// Author : Hao Chen
// Date   : 2020-07-26

/***************************************************************************************************** 
 *
 * 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? 
 * 
 * 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.
 * 	All local and domain names are non-empty.
 * 	Local names do not start with a '+' character.
 * 
 ******************************************************************************************************/

class Solution {
public:
    int numUniqueEmails(vector<string>& emails) {
        unordered_map<string, int> dict;
        for (auto& email : emails) {
            string addr;

            for(int i=0; i<email.size(); i++) {
                if (email[i] == '.' ) continue;

                if (email[i] == '+') {
                    while( email[++i] != '@');
                }
                if (email[i] =='@') {
                    addr += email.substr(i);
                    break;
                }
                addr += email[i];
            }

            dict[addr]++;
        }
        return dict.size();
    }

};