D
DevExCode

LeetCode 602: Friend Requests II: Who Has the Most Friends Solution

Master LeetCode problem 602 (Friend Requests II: Who Has the Most Friends), a medium challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

602. Friend Requests II: Who Has the Most Friends

Medium
Database

Problem Explanation

Explanation:

To solve this problem, we need to count the number of friends each person has by combining both the requester_id and accepter_id columns. We can achieve this by counting the occurrences of each person in these two columns. Then, we find the person with the maximum number of friends and output their id along with the count.

To find all people with the same maximum number of friends in the follow-up case, we need to store all people with the maximum friend count and output them at the end.

Algorithm:

  1. Create a HashMap to count the number of friends for each person.
  2. Iterate through the rows of the RequestAccepted table, incrementing the count for both the requester_id and accepter_id in the HashMap.
  3. Find the person with the maximum number of friends and store their id and count.
  4. Iterate through the HashMap to find all people with the same maximum friend count.
  5. Output the ids of all people with the maximum friend count.

Time Complexity:

The time complexity of this algorithm is O(n), where n is the number of rows in the RequestAccepted table.

Space Complexity:

The space complexity of this algorithm is O(n) for storing the counts of each person.

:

Solution Code

# Java Solution
SELECT user_id AS id, COUNT(*) AS num
FROM
    (SELECT requester_id AS user_id FROM RequestAccepted
     UNION ALL
     SELECT accepter_id AS user_id FROM RequestAccepted) AS temp
GROUP BY user_id
ORDER BY num DESC
LIMIT 1;

Try It Yourself

Loading code editor...

Related LeetCode Problems

Frequently Asked Questions

How to solve LeetCode 602 (Friend Requests II: Who Has the Most Friends)?

This page provides optimized solutions for LeetCode problem 602 (Friend Requests II: Who Has the Most Friends) in Java, C++, and Python, along with a detailed explanation and an interactive code editor to test your code.

What is the time complexity of LeetCode 602 (Friend Requests II: Who Has the Most Friends)?

The time complexity for LeetCode 602 (Friend Requests II: Who Has the Most Friends) varies by solution. Check the detailed explanation section for specific complexities in Java, C++, and Python implementations.

Can I run code for LeetCode 602 on DevExCode?

Yes, DevExCode provides an interactive code editor where you can write, test, and run your code for LeetCode 602 in Java, C++, or Python.

Back to LeetCode Solutions