0929-unique-email-addresses.js

/**
 * Built-in Functions Solution
 * Hash Set - Unique Emails
 * Time O(N * K) | Space O(N)
 * https://leetcode.com/problems/unique-email-addresses
 * @param {string[]} emails
 * @return {number}
 */
var numUniqueEmails = function (emails) {
    const valid = emails.map((email) => {
        const [local, domain] = email.split('@');
        return local.split('+').shift().split('.').join('') + '@' + domain;
    });

    return new Set(valid).size;
};

/**
 * Manual Solution
 * Hash Set - Unique Emails
 * Time O(N * K) | Space O(N)
 * https://leetcode.com/problems/unique-email-addresses
 * @param {string[]} emails
 * @return {number}
 */
var numUniqueEmails = function (emails) {
    const uniqEmails = new Set();

    for (let email of emails) {
        let cleanEmail = '';
        for (let i = 0; i < email.length; i++) {
            if (email[i] === '@') {
                cleanEmail += email.slice(i);
                break;
            } else if (email[i] === '+') {
                while (email[i] !== '@') i++;
                cleanEmail += email.slice(i);
                break;
            } else if (email[i] !== '.') {
                cleanEmail += email[i];
            }
        }

        uniqEmails.add(cleanEmail);
    }

    return uniqEmails.size;
};