leetcode-929-Unique-Email-Addresses

描述


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:

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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.

分析


邮箱地址分为两部分,前面一部分属于 local 字段,后面一部分属于 domain 字段,在 local 字段里,+ 符号后面的字符串需要丢弃,且 . 字符需要替换为空字符,最后用一个哈希集合来存储这些字段即可。

解决方案1(Java)


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class Solution {
public int numUniqueEmails(String[] emails) {
Set<String> result = new HashSet();
for (String email: emails) {
int atIndex = email.indexOf('@');
String local = email.substring(0, atIndex);
String domain = email.substring(atIndex);
if (local.contains("+")) {
local = local.substring(0, local.indexOf('+'));
}
local = local.replaceAll(".", "");
result.add(local + domain);
}
return result.size();
}
}

题目来源