The task was taken from leetcode
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.
My declarative solution
/**
* @param {string[]} emails
* @return {number}
*/
var numUniqueEmails = emails => {
return emails.reduce((validMails, mail) => {
const names = mail.split('@');
let [local, domain] = names;
const iPlus = [...local].findIndex(x => x === '+');
if (iPlus !== -1) { local = local.substr(0, iPlus); }
const key = local.split('.').join('') + '@' + domain;
if (!validMails.has(key)) { validMails.add(key); }
return validMails
}, new Set).size;
};
My Imperative solution
/**
* @param {string[]} emails
* @return {number}
*/
var numUniqueEmails2 = emails => {
const validMails = new Set();
for (const mail of emails) {
let [local, domain] = mail.split('@');
const iPlus = [...local].findIndex(x => x === '+');
if (iPlus !== -1) { local = local.substr(0, iPlus); }
const key = [...local].filter(x => x !== '.').join() + '@' + domain;
if (!validMails.has(key)) { validMails.add(key); }
}
return validMails.size;
};
My solution with regex
/**
* @param {string[]} emails
* @return {number}
*/
var numUniqueEmails3 = emails => {
const validMails = new Set();
for (const mail of emails) {
let [local, domain] = mail.split('@');
local = local.replace(/\+(.*)$/, '')
.replace(/\./g, '');
console.log(local);
const key = `${local}@${domain}`;
if (!validMails.has(key)) { validMails.add(key); }
}
return validMails.size;
};
Addendum
in numUniqueEmails
ran the code with this snippet:
const names = mail.split('@');
let [local, domain] = names;
and got 90th percentile. Running it again with this snippet:
let [local, domain] = mail.split('@');
gives me 25th percentile. I'd assume it should be the opposite. Does anyone know why this is the case and also how come the difference is so big?