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Java-based LeetCode algorithm problem solutions, regularly updated

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929\. Unique Email Addresses

Easy

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 `"[email protected]"`, `"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, `"[email protected]"` and `"[email protected]"` 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, `"[email protected]"` will be forwarded to `"[email protected]"`.

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 = ["[email protected]","[email protected]","[email protected]"]

**Output:** 2

**Explanation:** "[email protected]" and "[email protected]" actually receive mails.

**Example 2:**

**Input:** emails = ["[email protected]","[email protected]","[email protected]"]

**Output:** 3

**Constraints:**

*   `1 <= emails.length <= 100`
*   `1 <= emails[i].length <= 100`
*   `emails[i]` consist of lowercase English letters, `'+'`, `'.'` and `'@'`.
*   Each `emails[i]` contains exactly one `'@'` character.
*   All local and domain names are non-empty.
*   Local names do not start with a `'+'` character.
*   Domain names end with the `".com"` suffix.