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Design A Leaderboard

蓝哆啦呀 2022-03-11 阅读 61
leetcode

Design a Leaderboard class, which has 3 functions:

  1. addScore(playerId, score): Update the leaderboard by adding score to the given player's score. If there is no player with such id in the leaderboard, add him to the leaderboard with the given score.
  2. top(K): Return the score sum of the top K players.
  3. reset(playerId): Reset the score of the player with the given id to 0 (in other words erase it from the leaderboard). It is guaranteed that the player was added to the leaderboard before calling this function.

Initially, the leaderboard is empty.

Example 1:

Input: 
["Leaderboard","addScore","addScore","addScore","addScore","addScore","top","reset","reset","addScore","top"]
[[],[1,73],[2,56],[3,39],[4,51],[5,4],[1],[1],[2],[2,51],[3]]
Output: 
[null,null,null,null,null,null,73,null,null,null,141]

Explanation: 
Leaderboard leaderboard = new Leaderboard ();
leaderboard.addScore(1,73);   // leaderboard = [[1,73]];
leaderboard.addScore(2,56);   // leaderboard = [[1,73],[2,56]];
leaderboard.addScore(3,39);   // leaderboard = [[1,73],[2,56],[3,39]];
leaderboard.addScore(4,51);   // leaderboard = [[1,73],[2,56],[3,39],[4,51]];
leaderboard.addScore(5,4);    // leaderboard = [[1,73],[2,56],[3,39],[4,51],[5,4]];
leaderboard.top(1);           // returns 73;
leaderboard.reset(1);         // leaderboard = [[2,56],[3,39],[4,51],[5,4]];
leaderboard.reset(2);         // leaderboard = [[3,39],[4,51],[5,4]];
leaderboard.addScore(2,51);   // leaderboard = [[2,51],[3,39],[4,51],[5,4]];
leaderboard.top(3);           // returns 141 = 51 + 51 + 39;

思路:用hashmap去记录player的score,然后用pq去sort;

class Leaderboard {

    private HashMap<Integer, Integer> hashmap;
    public Leaderboard() {
        this.hashmap = new HashMap<>();
    }
    
    public void addScore(int playerId, int score) {
        this.hashmap.put(playerId, hashmap.getOrDefault(playerId, 0) + score);
    }
    
    public int top(int K) {
        PriorityQueue<Integer> pq = new PriorityQueue<Integer>((a, b) ->(b - a));
        for(Integer key: hashmap.keySet()) {
            pq.offer(hashmap.get(key));
        }
        int count = 0;
        int sum = 0;
        while(!pq.isEmpty() && K > 0) {
            sum += pq.poll();
            K--;
        }
        return sum;
    }
    
    public void reset(int playerId) {
        this.hashmap.put(playerId, 0);
    }
}

/**
 * Your Leaderboard object will be instantiated and called as such:
 * Leaderboard obj = new Leaderboard();
 * obj.addScore(playerId,score);
 * int param_2 = obj.top(K);
 * obj.reset(playerId);
 */

 

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