1348. Tweet Counts Per Frequency

https://leetcode.com/problems/tweet-counts-per-frequency/

Implement the class TweetCounts that supports two methods:

1. recordTweet(string tweetName, int time)

• Stores the tweetName at the recorded time (in seconds).

2. getTweetCountsPerFrequency(string freq, string tweetName, int startTime, int endTime)

• Returns the total number of occurrences for the given tweetName per minute, hour, or day (depending on freq) starting from the startTime (in seconds) and ending at the endTime (in seconds).

• freq is always minute, hour or day, representing the time interval to get the total number of occurrences for the given tweetName.

• The first time interval always starts from the startTime, so the time intervals are [startTime, startTime + delta*1>, [startTime + delta*1, startTime + delta*2>, [startTime + delta*2, startTime + delta*3>, ... , [startTime + delta*i, min(startTime + delta*(i+1), endTime + 1)> for some non-negative number i and delta (which depends on freq).

Example:

Input
["TweetCounts","recordTweet","recordTweet","recordTweet","getTweetCountsPerFrequency","getTweetCountsPerFrequency","recordTweet","getTweetCountsPerFrequency"]
[[],["tweet3",0],["tweet3",60],["tweet3",10],["minute","tweet3",0,59],["minute","tweet3",0,60],["tweet3",120],["hour","tweet3",0,210]]

Output
[null,null,null,null,[2],[2,1],null,[4]]

Explanation
TweetCounts tweetCounts = new TweetCounts();
tweetCounts.recordTweet("tweet3", 0);
tweetCounts.recordTweet("tweet3", 60);
tweetCounts.recordTweet("tweet3", 10);                             // All tweets correspond to "tweet3" with recorded times at 0, 10 and 60.
tweetCounts.getTweetCountsPerFrequency("minute", "tweet3", 0, 59); // return [2]. The frequency is per minute (60 seconds), so there is one interval of time: 1) [0, 60> - > 2 tweets.
tweetCounts.getTweetCountsPerFrequency("minute", "tweet3", 0, 60); // return [2, 1]. The frequency is per minute (60 seconds), so there are two intervals of time: 1) [0, 60> - > 2 tweets, and 2) [60,61> - > 1 tweet.
tweetCounts.recordTweet("tweet3", 120);                            // All tweets correspond to "tweet3" with recorded times at 0, 10, 60 and 120.
tweetCounts.getTweetCountsPerFrequency("hour", "tweet3", 0, 210);  // return [4]. The frequency is per hour (3600 seconds), so there is one interval of time: 1) [0, 211> - > 4 tweets.

Constraints:

• There will be at most 10000 operations considering both recordTweet and getTweetCountsPerFrequency.

• 0 <= time, startTime, endTime <= 10^9

• 0 <= endTime - startTime <= 10^4

实现两个api，recordTweet(string tweetName, int time)记录在什么时刻(单位s)有什么tweet，getTweetCountsPerFrequency(string freq, string tweetName, int startTime, int endTime)统计对于给定tweet，从startTime到endTime内以分或小时或天为间隔，出现的次数。time-based的遍历=>tree map。对于每个词维护一个的treemap，并在查询时根据interval划分出buckets，再从startTime开始遍历tree map并根据当前时间更新对应的bucket里的频率，直到超过endTime。

class TweetCounts {
public:
    TweetCounts() {}
    
    unordered_map<string, map<int, int>> m;
    void recordTweet(string tweetName, int time) {
        ++m[tweetName][time];
    }
    
    vector<int> getTweetCountsPerFrequency(string freq, string tweetName, int startTime, int endTime) {
        if (!m.count(tweetName)) return vector<int>();
        int delta = 60;
        if (freq[0] == 'h') delta = 3600;
        else if (freq[0] == 'd') delta = 86400;
        vector<int> res((endTime - startTime) / delta + 1);
        const auto &tm = m[tweetName];
        for (auto i = tm.lower_bound(startTime); i != tm.end() && i->first <= endTime; ++i) {
            res[(i->first - startTime) / delta] += i->second;
        }
        return res;
    }
};

/**
 * Your TweetCounts object will be instantiated and called as such:
 * TweetCounts* obj = new TweetCounts();
 * obj->recordTweet(tweetName,time);
 * vector<int> param_2 = obj->getTweetCountsPerFrequency(freq,tweetName,startTime,endTime);
 */