05 August 2008
Design a Leaderboard class, which has 3 functions:
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. top(K): Return the score sum of the top K players. 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;
Constraints:
1 <= playerId, K <= 10000 It’s guaranteed that K is less than or equal to the current number of players. 1 <= score <= 100 There will be at most 1000 function calls.
1.Use HashMap to record the people’s score
2.Use TreeMap to find the topK in O(klogn) by traverse the treemap
3.Reset we can just remove the key from the treemap which is O(log n), same for addScore().
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class Leaderboard {
Map<Integer, Integer> map;
TreeMap<Integer, Integer> sortedMap;
public Leaderboard() {
map = new HashMap<>();
sortedMap = new TreeMap<>(Collections.reverseOrder());
}
public void addScore(int playerId, int score) {
if (!map.containsKey(playerId)) {
map.put(playerId, score);
sortedMap.put(score, sortedMap.getOrDefault(score, 0) + 1);
} else {
int preScore = map.get(playerId);
sortedMap.put(preScore, sortedMap.get(preScore) - 1);
if (sortedMap.get(preScore) == 0) {
sortedMap.remove(preScore);
}
int newScore = preScore + score;
map.put(playerId, newScore);
sortedMap.put(newScore, sortedMap.getOrDefault(newScore, 0) + 1);
}
}
public int top(int K) {
int count = 0;
int sum = 0;
for (int key : sortedMap.keySet()) {
int times = sortedMap.get(key);
for (int i = 0; i < times; i++) {
sum += key;
count++;
if (count == K) {
break;
}
}
if (count == K) {
break;
}
}
return sum;
}
public void reset(int playerId) {
int preScore = map.get(playerId);
sortedMap.put(preScore, sortedMap.get(preScore) - 1);
if (sortedMap.get(preScore) == 0) {
sortedMap.remove(preScore);
}
map.remove(playerId);
}
}
/**
* 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);
*/