LeetCode 1244: Design A Leaderboard Solution

Master LeetCode problem 1244 (Design A Leaderboard), 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.

1244. Design A Leaderboard

Medium

Hash Table Design Sorting

Problem Explanation

Explanation:

To design a leaderboard, we can use a combination of data structures to efficiently store and update the scores of players. One approach is to use a HashMap to store the player IDs and their corresponding scores, and a TreeMap to maintain the scores in sorted order for efficient retrieval of the top K players.

Here's how we can design the leaderboard:

Use a HashMap to store the player IDs and their scores.
Use a TreeMap to store the scores as keys and a Set of player IDs with that score as values.
When updating a player's score, first remove the player's current score from the TreeMap and update the HashMap with the new score.
Update the TreeMap with the new score and player ID.
When retrieving the top K players, iterate through the TreeMap from highest to lowest score and add the player IDs to the result until reaching K.

Time complexity:

Inserting/Updating a player: O(logN) where N is the number of unique scores.
Retrieving the top K players: O(KlogN) where N is the number of unique scores.

Space complexity:

O(N) where N is the number of unique scores.

Solution Code

import java.util.*;

class Leaderboard {
    Map<Integer, Integer> scores;
    TreeMap<Integer, Set<Integer>> scoreCounts;

    public Leaderboard() {
        scores = new HashMap<>();
        scoreCounts = new TreeMap<>(Collections.reverseOrder());
    }

    public void addScore(int playerId, int score) {
        if (scores.containsKey(playerId)) {
            int prevScore = scores.get(playerId);
            scoreCounts.get(prevScore).remove(playerId);
            if (scoreCounts.get(prevScore).isEmpty()) {
                scoreCounts.remove(prevScore);
            }
        }
        scores.put(playerId, score);
        scoreCounts.putIfAbsent(score, new HashSet<>());
        scoreCounts.get(score).add(playerId);
    }

    public int top(int K) {
        int total = 0;
        for (int key : scoreCounts.keySet()) {
            Set<Integer> players = scoreCounts.get(key);
            for (int player : players) {
                total++;
                if (total > K) break;
            }
            if (total > K) break;
        }
        return total;
    }
}

Try It Yourself

Loading code editor...

Frequently Asked Questions

How to solve LeetCode 1244 (Design A Leaderboard)?

This page provides optimized solutions for LeetCode problem 1244 (Design A Leaderboard) 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 1244 (Design A Leaderboard)?

The time complexity for LeetCode 1244 (Design A Leaderboard) varies by solution. Check the detailed explanation section for specific complexities in Java, C++, and Python implementations.

Can I run code for LeetCode 1244 on DevExCode?

Yes, DevExCode provides an interactive code editor where you can write, test, and run your code for LeetCode 1244 in Java, C++, or Python.

Back to LeetCode Solutions