## Algorithm

Problem Name: 929. 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 <= 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.

## 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;
}
};
``````
Copy The Code &

Input

cmd
emails = ["test.email+alex@leetcode.com","test.e.mail+bob.cathy@leetcode.com","testemail+david@lee.tcode.com"]

Output

cmd
2

### #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];
}
}
``````
Copy The Code &

Input

cmd
emails = ["test.email+alex@leetcode.com","test.e.mail+bob.cathy@leetcode.com","testemail+david@lee.tcode.com"]

Output

cmd
2

### #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]
}
}
}
``````
Copy The Code &

Input

cmd
emails = ["a@leetcode.com","b@leetcode.com","c@leetcode.com"]

Output

cmd
3

### #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('.', '')
return len(rec)
``````
Copy The Code &

Input

cmd
emails = ["a@leetcode.com","b@leetcode.com","c@leetcode.com"]

Output

cmd
3

### #5 Code Example with C# Programming

```Code - C# Programming```

``````
using System.Collections.Generic;

namespace LeetCode
{
{
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(".", "");

}

return hashSet.Count;
}
}
}
``````
Copy The Code &

Input

cmd
emails = ["a@leetcode.com","b@leetcode.com","c@leetcode.com"]

Output

cmd
3