Lc0929

05 August 2008

929 Unique Email Address

题目

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

For example, in 
1

alice@leetcode.com
, 
1

alice
is the local name, and 
1

leetcode.com
is the domain name.

Besides lowercase letters, these emails may contain 
1

'.'
s or 
1

'+'
s.

If you add periods (
1

'.'
) 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, 
1

"alice.z@leetcode.com"
and 
1

"alicez@leetcode.com"
forward to the same email address. (Note that this rule does not apply for domain names.)

If you add a plus (
1

'+'
) in the local name, everything after the first plus sign will be ignored. This allows certain emails to be filtered, for example 
1

m.y+name@email.com
will be forwarded to 
1

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 
1

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

Example 1:

1
2
3

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:

分析

根据题意，”.”可以忽略，”+”在名字的位置后面的忽略，domain name照常比较。

直接的思路，用hashset除重。

代码

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class Solution {
    public int numUniqueEmails(String[] emails) {
        HashSet<String> set = new HashSet<>();
        int count = 0;
        for (String email : emails) {
            String[] arr = email.split("@", 2); // @只出现一次
            StringBuilder sb = new StringBuilder();
            int index = 0;
            while (index < arr[0].length() && arr[0].charAt(index) != '+') {
                if (arr[0].charAt(index) != '.') {
                    sb.append(arr[0].charAt(index));
                }
                index++;
            }
            sb.append("@");
            sb.append(arr[1]);
            if (set.add(sb.toString())) {
                count++;
            }
        }
        return count;
    }
} 

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class Solution {
    public int numUniqueEmails(String[] emails) {
        if (emails == null || emails.length == 0) {
            return 0;
        }
        Set<String> result = new HashSet<>();
        for (String email : emails) {
            StringBuilder sb = new StringBuilder();
            String[] splitted = email.split("\\@");
            char[] letters = splitted[0].toCharArray();
            for (char letter : letters) {
                if (letter != '+') {
                    if (Character.isLetterOrDigit(letter)) {
                        sb.append(letter);
                    } else if (letter == '.') {
                        continue;
                    }
                } else {
                    break;
                }
            }
            if (!sb.toString().isEmpty()) {
                sb.append(splitted[1]);
                result.add(sb.toString());
            }
        }
        return result.size();
    }
}