Create Unique_email_address.md

[nittoco]

問題文URL: https://leetcode.com/problems/unique-email-addresses/description/
Every valid email consists of a local name and a domain name, separated by the '@' sign. Besides lowercase letters, the email may contain one or more '.' or '+'.

For example, in "alice@leetcode.com", "alice" is the local name, and "leetcode.com" is the domain name.
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. Note that this rule does not apply to domain names.

For example, "alice.z@leetcode.com" and "alicez@leetcode.com" forward to the same email address.
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. Note that this rule does not apply to domain names.

For example, "m.y+name@email.com" will be forwarded to "my@email.com".
It is possible to use both of these rules at the same time.

Given an array of strings emails where we send one email to each emails[i], return the number of different addresses that actually receive mails.

Example 1:

Input: emails = ["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.
Example 2:

Input: emails = ["a@leetcode.com","b@leetcode.com","c@leetcode.com"]
Output: 3

[nodchip]

特に忌避感は感じませんでした。

[nodchip]

email_set の _set は、変数の型に含まれているため、情報が重複しています。外したほうが良いと思います。 unique_emails はいかがでしょうか？

[nodchip]

['ab@c', 'a@bc'] のときに正しい解を返さないように思いました。

[nittoco]

これ気づいてませんでした。ありがとうございます

[nodchip]

print すると、実行時に標準出力を汚してしまいます。意図して行う場合以外は、提出する前、またはレビューする前に削除しましょう。

[oda]

split 2回はちょっと違和感ですね。上みたいに
local_name, domain_name = email.split('@', 1)
のほうがいいでしょう。