How do you solve Find Valid Emails on LeetCode?

Find Valid Emails (LeetCode #3436) 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: Using regex can simplify validation checks.

What is the brute force solution for Find Valid Emails?

The brute force approach for Find Valid Emails is Brute Force, with O(n²) time complexity and O(1) space complexity. The brute force approach checks each email one by one against the criteria for validity. It’s straightforward but can be inefficient as it may involve multiple checks for each email. The optimal Optimal Solution approach improves this to O(n).

What algorithm or data structure is used to solve Find Valid Emails?

Find Valid Emails uses the following concepts: Database. The recommended patterns to study are: Regular Expressions, String Manipulation.

What are the interview tips for Find Valid Emails?

Always clarify the requirements before starting to code. Discuss your thought process and approach with the interviewer. Consider edge cases and test your solution against them.

What are common mistakes when solving Find Valid Emails?

Not considering edge cases like multiple '@' symbols. Overlooking the importance of the domain part.

#3436

Find Valid Emails

Easy

DatabaseRegular ExpressionsString Manipulation

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 uses a single pass through the emails while applying regular expressions to validate the format. This reduces the number of checks and improves efficiency.

⚙️

Algorithm

4 steps

1Step 1: Use a regular expression to match the valid email format in one go.
2Step 2: The regex checks for exactly one '@', valid local part, and valid domain ending with '.com'.
3Step 3: Select valid emails directly using the regex match.
4Step 4: Order the results by user_id.

solution.py1 lines

1SELECT user_id, email FROM Users WHERE email REGEXP '^[A-Za-z0-9_]+@[A-Za-z]+\.com$' ORDER BY user_id;

ℹ

Complexity note: The time complexity is O(n) because we are scanning through the list of emails once and applying a regex match which is efficient for this case.

1Using regex can simplify validation checks.
2Validating emails requires careful attention to format.

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