力扣排行榜

import java.util.HashMap;
import java.util.Map;

public class Leaderboard {
    private Map<Integer, Integer> scores;

    /**
     * Constructor to initialize the leaderboard.
     */
    public Leaderboard() {
        scores = new HashMap<>();
    }

    /**
     * Add score for the player. If the player does not exist, add the player with initial score.
     * @param playerId Player's unique ID.
     * @param score The score to add.
     */
    public void addScore(int playerId, int score) {
        scores.put(playerId, scores.getOrDefault(playerId, 0) + score);
    }

    /**
     * Return the sum of the top K scores using Java Streams.
     * @param K Number of top scores to sum.
     * @return Sum of the top K scores.
     */
    public int top(int K) {
        return scores.values().stream()
                .sorted((a, b) -> b - a)
                .limit(K)
                .mapToInt(Integer::intValue)
                .sum();
    }

    /**
     * Reset the score of the player to zero.
     * @param playerId Player's unique ID.
     */
    public void reset(int playerId) {
        scores.remove(playerId);
    }
}