Algorithm
Problem Name: 929. Unique Email Addresses
Problem Link: https://leetcode.com/problems/unique-email-addresses/
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
Constraints:
1 <= emails.length <= 1001 <= emails[i].length <= 100emails[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.
Code Examples
#1 Code Example with C++ Programming
Code -
C++ Programming
class Solution {
public:
int numUniqueEmails(vector<string>& emails) {
unordered_setres;
for (const string& s: emails) {
string e = filter(s);
res.insert(e);
}
return res.size();
}
string filter(const string& email) {
string res;
int i = 0, n = email.size();
bool ignore = false;
for (; i < n; ++i) {
if (email[i] == '@') {
break;
} else if (ignore || email[i] == '.') {
continue;
} else if (email[i] == '+') {
ignore = true;
}
res.push_back(email[i]);
}
for (; i < n; ++i) {
res.push_back(email[i]);
}
return res;
}
};
Input
Output
#2 Code Example with Java Programming
Code -
Java Programming
class Solution {
public int numUniqueEmails(String[] emails) {
return Arrays.stream(emails).map(Solution::getFormattedEmail).collect(Collectors.toSet()).size();
}
private static String getFormattedEmail(String email) {
String[] strs = email.split("@");
int plusIdx = strs[0].indexOf('+');
String formattedLocalName = strs[0].substring(0, (plusIdx == -1 ? strs[0].length() : plusIdx))
.replaceAll("\\.", "");
return formattedLocalName + "@" + strs[1];
}
}
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Output
#3 Code Example with Javascript Programming
Code -
Javascript Programming
const numUniqueEmails = function(emails) {
const res = new Set()
emails.forEach(el => helper(el, res))
return res.size
};
function helper(str, s) {
const arr = str.split('@')
const p = arr[0]
const d = arr[1]
let res = ''
for(let i = 0, len = p.length; i < len; i++) {
if(p[i] === '.') {
continue
} else if(p[i] === '+') {
break
} else {
res += p[i]
}
}
s.add(`${res}@${d}`)
}
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Output
#4 Code Example with Python Programming
Code -
Python Programming
class Solution:
def numUniqueEmails(self, emails: List[str]) -> int:
rec = set()
for email in emails:
local, domain = email.split('@')
local = local.split('+')[0].replace('.', '')
rec.add(local + '@' + domain)
return len(rec)
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Output
#5 Code Example with C# Programming
Code -
C# Programming
using System.Collections.Generic;
namespace LeetCode
{
public class _0929_UniqueEmailAddresses
{
public int NumUniqueEmails(string[] emails)
{
var hashSet = new HashSet < string>();
foreach (var email in emails)
{
var at_index = email.IndexOf('@');
var local = email.Substring(0, at_index);
var domain = email.Substring(at_index);
var plus_index = local.IndexOf('+');
if (plus_index >= 0)
local = local.Substring(0, plus_index);
local = local.Replace(".", "");
hashSet.Add(local + domain);
}
return hashSet.Count;
}
}
}
Input
Output