# LeetCode 929. Unique Email Addresses

## Description

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.

## Explanation

Get all email real local names first (real local name + “@” + domain). Then count uniques.

## Python Solution

``````class Solution:
def numUniqueEmails(self, emails: List[str]) -> int:
uniques = set()

for email in emails:
real_email = self.get_real_email(email)

return len(uniques)

def get_real_email(self, email):
local_name, domain = email.split('@')
local_name = local_name.split('+')[0]
local_name = local_name.replace('.', '')

return local_name + '@' + domain
``````
• Time complexity: ~N
• Space complexity: ~N

## 2 Thoughts to “LeetCode 929. Unique Email Addresses”

1. Tom says:

Hi,

Can you do LeetCode 364: Nested List Weight Sum II
LeetCode 339: Nested List Weight Sum? Thanks