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➤微信公众号：山青咏芝（shanqingyongzhi）
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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 <= 1001 <= emails.length <= 100- Each
emails[i]contains exactly one'@'character.
每封电子邮件都由一个本地名称和一个域名组成，以 @ 符号分隔。
例如，在 alice@leetcode.com中， alice 是本地名称，而 leetcode.com 是域名。
除了小写字母，这些电子邮件还可能包含 ',' 或 '+'。
如果在电子邮件地址的本地名称部分中的某些字符之间添加句点（'.'），则发往那里的邮件将会转发到本地名称中没有点的同一地址。例如，"alice.z@leetcode.com” 和 “alicez@leetcode.com” 会转发到同一电子邮件地址。 （请注意，此规则不适用于域名。）
如果在本地名称中添加加号（'+'），则会忽略第一个加号后面的所有内容。这允许过滤某些电子邮件，例如 m.y+name@email.com 将转发到 my@email.com。 （同样，此规则不适用于域名。）
可以同时使用这两个规则。
给定电子邮件列表 emails，我们会向列表中的每个地址发送一封电子邮件。实际收到邮件的不同地址有多少？
示例：
输入：["test.email+alex@leetcode.com","test.e.mail+bob.cathy@leetcode.com","testemail+david@lee.tcode.com"] 输出：2 解释：实际收到邮件的是 "testemail@leetcode.com" 和 "testemail@lee.tcode.com"。
提示：
1 <= emails[i].length <= 1001 <= emails.length <= 100- 每封
emails[i]都包含有且仅有一个'@'字符。
412ms
1 class Solution {
2 func numUniqueEmails(_ emails: [String]) -> Int {
3 var es:Set<String> = Set<String>()
4 for e in emails
5 {
6 //分割字符串
7 var s: Array = e.components(separatedBy: "@")
8 var str:String = String(s[0])
9 //字符串替换
10 str = str.replacingOccurrences(of: ".", with: "")
11 //字符查找，返回字符索引
12 var ind = str.firstIndex(of: "+") ?? s[0].endIndex
13 if ind != str.endIndex
14 {
15 //截取子字符串
16 str = String(str[..<ind])
17 }
18 //拼接字符串,Set添加用.insert
19 es.insert(str + "@" + s[1])
20 }
21 return es.count
22 }
23 }
140ms
1 class Solution {
2 func numUniqueEmails(_ emails: [String]) -> Int {
3 var dict = Dictionary<String,Set<String>>()
4 emails.forEach { (email) in
5 let strings = email.split(separator: "@")
6 var address:String = String(String(strings.first!).split(separator: "+").first!)
7 address = address.split(separator: ".").joined()
8 let domain = String(strings[1])
9 if dict[domain] == nil {
10 dict[domain] = Set<String>.init([address])
11 }else{
12 var set = dict[domain]
13 set?.insert(address)
14 dict[domain] = set
15 }
16 }
17 var count = 0
18 //print(dict)
19 dict.values.forEach { (set) in
20 count += set.count
21 }
22 return count
23 }
24 }
144ms
1 class Solution {
2 func numUniqueEmails(_ emails: [String]) -> Int {
3
4 var uniqAddresses = [String]()
5 for emails in emails {
6 let shrinkedEmailAddress = shrinkTheEmailAddress(emails)
7 if uniqAddresses.contains(shrinkedEmailAddress) {
8 continue
9 } else {
10 uniqAddresses.append(shrinkedEmailAddress)
11 }
12 }
13 return uniqAddresses.count
14 }
15
16 fileprivate func shrinkTheEmailAddress(_ address: String) -> String {
17 let chars = Array(address)
18 var plusIndex = 0
19 var atIndex = 0
20 for i in 0 ..< chars.count {
21 if chars[i] == "+" && plusIndex == 0 {
22 plusIndex = i
23 }
24 if chars[i] == "@" {
25 atIndex = i
26 }
27 }
28
29 var result = ""
30 for i in 0..<plusIndex {
31 if chars[i] == "." {
32 continue
33 }
34 result += String(chars[i])
35 }
36 for i in atIndex + 1..<chars.count {
37 result += String(chars[i])
38 }
39 return result
40 }
41 }
168ms
1 class Solution {
2 func numUniqueEmails(_ emails: [String]) -> Int {
3 var set = Set<String>()
4 for email in emails {
5 set.insert(filter(email: email))
6 }
7 return set.count
8 }
9
10
11 func filter(email: String) -> String {
12 var result = ""
13 var inPrefix = true
14 var lookingForAt: Bool = false
15 for char in Array(email) {
16 let character = String(char)
17
18 if lookingForAt && character != "@" { continue }
19 if character == "." && inPrefix { continue }
20 if character == "@" {
21 inPrefix = false
22 lookingForAt = false
23 }
24
25 if character == "+" && inPrefix {
26 lookingForAt = true
27 continue
28 }
29 result += character
30 }
31 return result
32 }
33 }
192ms
1 class Solution {
2 func numUniqueEmails(_ emails: [String]) -> Int {
3 var uniqueEmails = Set<String>()
4
5 for email in emails {
6 let emailComponents = email.split(separator: "@")
7 let usernameComponents = emailComponents[0].split(separator: "+")
8
9 var username = usernameComponents[0]
10 let domain = emailComponents[1]
11
12 username.removeAll { $0 == "." }
13
14 let uniqueEmail = String(username + "@" + domain)
15
16 guard !uniqueEmails.contains(uniqueEmail) else { continue }
17 uniqueEmails.insert(uniqueEmail)
18 }
19
20 return uniqueEmails.count
21 }
22 }
296ms
1 class Solution {
2
3 struct EmailCharacter {
4 static let plus: Character = "+"
5 static let atTheRate: Character = "@"
6 static let dot: Character = "."
7 }
8
9 func numUniqueEmails(_ emails: [String]) -> Int {
10
11 var emailAddresses = Set<String>()
12
13 for email in emails {
14 let emailParts = email.split(separator: EmailCharacter.atTheRate)
15 if emailParts.count == 2 {
16 let localName = String(emailParts[0])
17 let domainName = String(emailParts[1])
18 if let sanitizedLocalName = self.sanitizedLocalName(localName) {
19 emailAddresses.insert(sanitizedLocalName + domainName)
20 }
21 } else {
22 continue
23 }
24 }
25
26 return emailAddresses.count
27 }
28
29 func sanitizedLocalName(_ localName: String) -> String? {
30 let localName = localName.replacingOccurrences(of: String(EmailCharacter.dot), with: "", options: NSString.CompareOptions.literal, range: nil)
31 let names = localName.split(separator: EmailCharacter.plus)
32
33 guard names.count > 0 else {
34 return localName
35 }
36
37 let firstSplitName = names[0]
38 if firstSplitName.hasPrefix(String(EmailCharacter.plus)) {
39 return localName
40 }
41
42 return String(firstSplitName)
43 }
44
45 }