0929-unique-email-addresses.js

/**
 * 929. Unique Email Addresses
 * https://leetcode.com/problems/unique-email-addresses/
 * Difficulty: Easy
 *
 * 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?
 */

/**
 * @param {string[]} emails
 * @return {number}
 */
var numUniqueEmails = function(emails) {
  return new Set(emails.map(e => e.replace(/\.(?=[\w\.+]+@)|\+[\w.+]+(?=@)/g, ''))).size;
};