[leetcode] 929. Unique Email Addresses @ python

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