[leetcode] 929. Unique Email Addresses @ python

最新推荐文章于 2021-08-12 21:54:08 发布

原创最新推荐文章于 2021-08-12 21:54:08 发布 · 272 阅读

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本文探讨了电子邮件地址的解析技巧，重点介绍了如何处理带有特殊字符的本地名称部分，如'.'和'+'，并解释了如何根据特定规则过滤和标准化这些地址。通过实例演示，我们展示了如何使用Python实现一个算法，该算法可以去除重复的邮件地址，只保留实际接收邮件的不同地址数量。

原题

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

Note:

1 <= emails[i].length <= 100
1 <= emails.length <= 100
Each emails[i] contains exactly one ‘@’ character.

解法

字符串处理. 构造一个字典d存放每个domain对应的local name, 遍历emails, 将domain和local name分离出来, local name进行处理, 将不重复的local name加入字典. 最后遍历字典的键, 将值的长度相加.
Time: O(n)
Space: O(n)

代码

class Solution(object):
    def numUniqueEmails(self, emails):
        """
        :type emails: List[str]
        :rtype: int
        """
        d = collections.defaultdict(list)
        for email in emails:            
            i = email.index('@')
            local = email[:i]
            domain = email[i+1:]
            # process local name
            local = local.replace('.', '')
            if '+' in local:
                index = local.index('+')
                local = local[:index]
            # process address
            if local not in d[domain]:
                d[domain].append(local)
        ans = 0
        for key in d:
            ans += len(d[key])
        return ans