LeetCode 1244. 力扣排行榜（map+multiset）

示例 1：
输入： 
["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]]
输出：
[null,null,null,null,null,null,73,null,null,null,141]
解释： 
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;
 
提示：
1 <= playerId, K <= 10000
题目保证 K 小于或等于当前参赛者的数量
1 <= score <= 100
最多进行 1000 次函数调用

struct cmp
{
	bool operator()(int a, int b) const
	{
		return a > b;
	}
};
class Leaderboard {
	unordered_map<int,int> m;//id，score
	multiset<int, cmp> topk;//分数，降序排列
public:
    Leaderboard() {

    }
    
    void addScore(int playerId, int score) {
    	if(m.find(playerId) == m.end())
    	{
    		m[playerId] = score;
            topk.insert(score);
    	}
    	else
    	{
            auto it = topk.find(m[playerId]);
            topk.erase(it);//删除分数
            m[playerId] += score;
            topk.insert(m[playerId]);//更新分数
        }
    }
    
    int top(int K) {
    	int sum = 0;
    	for(auto it = topk.begin(); it != topk.end() && K; ++it)
    	{
            K--;
    		sum += (*it);
    	}
    	return sum;
    }
    
    void reset(int playerId) {
        auto it = topk.find(m[playerId]);
        topk.erase(it);
    	m[playerId] = 0;
        topk.insert(0);
    }
};