校园内的汽车

https://www.acwing.com/problem/content/description/1587/

思路：
电话记录的模型，先筛选出所有符合要求的记录，之后按照题目要求做即可。

#include <iostream>
#include <cstring>
#include <algorithm>
#include <unordered_map>
#include <vector>

using namespace std;

struct Event
{
    int tm, status;

    bool operator< (const Event &t) const
    {
        return tm < t.tm;
    }
};

int get(vector<Event>& ets)
{
    int res = 0;
    for (int i = 0; i < ets.size(); i += 2)
        res += ets[i + 1].tm - ets[i].tm;

    return res;
}

int main()
{
    int n, m;
    scanf("%d%d", &n, &m);

    unordered_map<string, vector<Event>> cars;

    char id[10], status[10];
    for (int i = 0; i < n; i ++ )
    {
        int hh, mm, ss;
        scanf("%s %d:%d:%d %s", id, &hh, &mm, &ss, status);
        int t = hh * 3600 + mm * 60 + ss;
        int s = 0;
        if (status[0] == 'o') s = 1;
        cars[id].push_back({t, s});
    }

    vector<Event> events;
    for (auto& item : cars)
    {
        auto& ets = item.second;
        sort(ets.begin(), ets.end());
        int k = 0;

        for (int i = 0; i < ets.size(); i ++ )
            if (ets[i].status == 0)
            {
                if (i + 1 < ets.size() && ets[i + 1].status == 1)
                {
                    ets[k ++ ] = ets[i];
                    ets[k ++ ] = ets[i + 1];
                    i ++ ;
                }
            }

        ets.erase(ets.begin() + k, ets.end());
        for (int i = 0; i < k; i ++ ) events.push_back(ets[i]);
    }

    sort(events.begin(), events.end());

    int k = 0, sum = 0;
    while (m -- )
    {
        int hh, mm, ss;
        scanf("%d:%d:%d", &hh, &mm, &ss);
        int t = hh * 3600 + mm * 60 + ss;

        while (k < events.size() && events[k].tm <= t)
        {
            if (events[k].status == 0) sum ++ ;
            else sum -- ;
            k ++ ;
        }

        printf("%d\n", sum);
    }

    int maxt = 0;
    for (auto& item : cars) maxt = max(maxt, get(item.second));

    vector<string> res;
    for (auto& item : cars)
        if (get(item.second) == maxt)
            res.push_back(item.first);

    sort(res.begin(), res.end());

    for (int i = 0; i < res.size(); i ++ ) printf("%s ", res[i].c_str());

    printf("%02d:%02d:%02d\n", maxt / 3600, maxt % 3600 / 60, maxt % 60);

    return 0;
}