LeetCode之Unique Email Addresses（Kotlin）

问题： 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
复制代码

---

方法： 遇到"."跳过，遇到"+"跳事后面字符，遇到@忽略规则，用set保存按规则过滤的字符，最后输出set的size即为结果。

具体实现：

class UniqueEmailAddresses {
    fun numUniqueEmails(emails: Array<String>): Int {
        val set = mutableSetOf<String>()
        for (email in emails) {
            val sb = StringBuilder()
            var ignore = false
            var skip = false
            for (ch in email) {
                if (!ignore) {
                    if(ch == '@') {
                        ignore = true
                        skip = false
                    } else if(ch == '.' || skip) {
                        continue
                    } else if (ch == '+') {
                        skip = true
                    }
                }
                sb.append(ch)
            }
            set.add(sb.toString())
        }
        return set.size
    }
}

fun main(args: Array<String>) {
    val input = arrayOf("test.email+alex@leetcode.com","test.e.mail+bob.cathy@leetcode.com","testemail+david@lee.tcode.com")
    val uniqueEmailAddresses = UniqueEmailAddresses()
    println(uniqueEmailAddresses.numUniqueEmails(input))
}
复制代码

有问题随时沟通

具体代码实现能够参考Github