Java Coding Interview(non-leetcode-style) - Top 10 Active Users by Login & Email Trust

Solving non-leetcode style Java coding problems

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Problem

You’re building a user analytics system. Given a list of users, your task is to select the top 10 trusted active users based on certain rules.

User class:

Requirements:

Write a method:

public List<String> getTop10TrustedActiveEmails(List<User> users)

that returns a list of up to 10 email addresses satisfying all of the following logic:

Filtering Rules: Only include users where:

• isActive == true

• email != null, lastLoginDate != null

• lastLoginDate is within the last 30 days from today

• loginCountLast30Days >= 5

Deduplication Rules: Deduplicate by email.

• If the same email appears more than once, keep the one with:
  - The latest lastLoginDate
- If tied, choose the one with emailVerified == true
- If tied again, choose the one with the highest loginCountLast30Days
- If still tied, choose the lexicographically smaller userId

Final Ranking:

Sort the resulting users by:

• loginCountLast30Days descending

• Then by lastLoginDate descending

Return:

• A list of email addresses (no duplicates)

• Max size: 10

Solution

Filter Active Users