Introduction

In this blog post, we will explore how to solve the LeetCode problem "929" using AI. LeetCode is a popular platform for preparing for coding interviews, and with the help of AI tools like Chatmagic, we can generate solutions quickly and efficiently - helping you pass the interviews and get the job offer without having to study for months.

Problem Statement

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. Domain names must contain at least one character before ".com" suffix.

Explanation

• Parse and Normalize: For each email, split it into local and domain parts. Normalize the local part by removing periods and everything after the first plus sign.
  • Store Unique Addresses: Use a set to store the normalized email addresses to count only the distinct ones.
  • Return Count: Return the size of the set, which represents the number of different addresses that receive mails.

• Runtime Complexity: O(N M), where N is the number of emails and M is the maximum length of an email. Storage Complexity: O(N M) in the worst case, to store the normalized emails in the set.

Code

    def numUniqueEmails(emails):
    """
    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.
    Domain names must contain at least one character before ".com" suffix.
    """

    unique_emails = set()

    for email in emails:
        local_name, domain_name = email.split('@')
        local_name = local_name.split('+')[0].replace('.', '')
        unique_emails.add(local_name + '@' + domain_name)

    return len(unique_emails)