How do you solve Find Users With Valid E-Mails on LeetCode?

Find Users With Valid E-Mails (LeetCode #1517) can be solved using Brute Force or Optimal Solution. The optimal approach is Optimal Solution with O(n) time complexity and O(n) space complexity. Key insight: Emails must end with '@leetcode.com'.

What is the brute force solution for Find Users With Valid E-Mails?

The brute force approach for Find Users With Valid E-Mails is Brute Force, with O(n²) time complexity and O(1) space complexity. In the brute force approach, we will check each email one by one to see if it meets the criteria for being valid. This involves checking if the email contains the correct domain and if the prefix is valid according to the specified rules. The optimal Optimal Solution approach improves this to O(n).

What algorithm or data structure is used to solve Find Users With Valid E-Mails?

Find Users With Valid E-Mails uses the following concepts: Database. The recommended patterns to study are: Regex, String Matching.

What are the interview tips for Find Users With Valid E-Mails?

Understand the requirements clearly before coding. Practice writing SQL queries to become comfortable with pattern matching. Be prepared to explain your thought process and why you chose a particular approach.

What are common mistakes when solving Find Users With Valid E-Mails?

Not using regex properly to validate the prefix. Forgetting to check the domain.

#1517

Find Users With Valid E-Mails

Easy

DatabaseRegexString Matching

LeetCode ↗

Approaches

Brute ForceOptimal

Complexity Comparison

	Brute Force	Optimal Solution★
Time	O(n²)	O(n)
Space	O(1)	O(n)

💡

Intuition

Time O(n)Space O(n)

The optimal solution leverages SQL's pattern matching capabilities to efficiently filter valid emails in a single query, reducing the need for multiple checks.

⚙️

Algorithm

3 steps

1Step 1: Use a SQL query to select users whose emails end with '@leetcode.com'.
2Step 2: Use a regular expression to ensure the prefix starts with a letter and contains only valid characters.
3Step 3: Return the user_id, name, and mail of valid users.

solution.py1 lines

1SELECT user_id, name, mail FROM Users WHERE mail LIKE '%@leetcode.com' AND mail REGEXP '^[A-Za-z][A-Za-z0-9_.-]*@leetcode.com';

ℹ

Complexity note: The time complexity is O(n) because we are scanning through the list of users once, applying the regex and LIKE conditions in a single pass.

1Emails must end with '@leetcode.com'.
2The prefix must start with a letter and contain valid characters.

Solutions and explanations are original Tejav content. Problem titles © LeetCode — use the LeetCode button above for the full problem statement.