PAT A1095 Cars on Campus （30 分）——排序，时序，从头遍历会超时

Zhejiang University has 8 campuses and a lot of gates. From each gate we can collect the in/out times and the plate numbers of the cars crossing the gate. Now with all the information available, you are supposed to tell, at any specific time point, the number of cars parking on campus, and at the end of the day find the cars that have parked for the longest time period.

Input Specification:

Each input file contains one test case. Each case starts with two positive integers N (≤10​4​​), the number of records, and K (≤8×10​4​​) the number of queries. Then N lines follow, each gives a record in the format:

plate_number hh:mm:ss status

where plate_number is a string of 7 English capital letters or 1-digit numbers; hh:mm:ss represents the time point in a day by hour:minute:second, with the earliest time being 00:00:00 and the latest 23:59:59; and status is either in or out.

Note that all times will be within a single day. Each in record is paired with the chronologically next record for the same car provided it is an out record. Any in records that are not paired with an out record are ignored, as are out records not paired with an in record. It is guaranteed that at least one car is well paired in the input, and no car is both in and out at the same moment. Times are recorded using a 24-hour clock.

Then K lines of queries follow, each gives a time point in the format hh:mm:ss. Note: the queries are given in ascending order of the times.

Output Specification:

For each query, output in a line the total number of cars parking on campus. The last line of output is supposed to give the plate number of the car that has parked for the longest time period, and the corresponding time length. If such a car is not unique, then output all of their plate numbers in a line in alphabetical order, separated by a space.

Sample Input:

16 7
JH007BD 18:00:01 in
ZD00001 11:30:08 out
DB8888A 13:00:00 out
ZA3Q625 23:59:50 out
ZA133CH 10:23:00 in
ZD00001 04:09:59 in
JH007BD 05:09:59 in
ZA3Q625 11:42:01 out
JH007BD 05:10:33 in
ZA3Q625 06:30:50 in
JH007BD 12:23:42 out
ZA3Q625 23:55:00 in
JH007BD 12:24:23 out
ZA133CH 17:11:22 out
JH007BD 18:07:01 out
DB8888A 06:30:50 in
05:10:00
06:30:50
11:00:00
12:23:42
14:00:00
18:00:00
23:59:00

Sample Output:

1
4
5
2
1
0
1
JH007BD ZD00001 07:20:09

 #include <stdio.h>
 #include <algorithm>
 #include <set>
 //#include <string.h>
 #include <vector>
 //#include <math.h>
 #include <queue>
 #include <iostream>
 #include <string>
 #include <map>
 using namespace std;
 const int maxn = ;
 const int inf = ;
 int n,k,m,l;
 struct node{
     string id;
     int time,status;
 };
 vector<node> v,valid;
 bool cmp(const node &a,const node &b){
     return a.id==b.id?a.time<b.time:a.id<b.id;
 }
 bool cmp2(const node &a,const node &b){
     return a.time<b.time;
 }
 map<string,int> mp;
 int main(){
     scanf("%d %d",&n,&k);
     for(int i=;i<n;i++){
         string id,sta;
         int h,m,s;
         cin>>id;
         scanf("%d:%d:%d ",&h,&m,&s);
         cin>>sta;
         int time = *h+*m+s;
         node tmp;
         tmp.id=id;
         tmp.time=time;
         int status=;
         if(sta=="out") status=;
         tmp.status=status;
         v.push_back(tmp);
     }
     sort(v.begin(),v.end(),cmp);
     int longest=;
     for(int i=;i<n-;i++){
         if(v[i].id == v[i+].id && v[i].status== && v[i+].status==){
             valid.push_back(v[i]);
             valid.push_back(v[i+]);
             mp[v[i].id] += v[i+].time - v[i].time;
             if(mp[v[i].id]>longest) longest = mp[v[i].id];
         }
     }
     sort(valid.begin(),valid.end(),cmp2);
     int pos=,res=;
     for(int j=;j<k;j++){
         int h,m,s;
         scanf("%d:%d:%d",&h,&m,&s);
         int time = *h+*m+s;
         //int res=0;
         for(int i=pos;i<valid.size();i++){
             if(valid[i].time<=time){
                 if(valid[i].status==) res++;
                 else res--;
             }
             else{
                 pos=i;
                 break;
             }
         }
         printf("%d\n",res);
     }
     vector<string> maxs;
     for(auto it:mp){
         if(it.second==longest){
             maxs.push_back(it.first);
         }
     }
     for(int i=;i<maxs.size();i++){
         printf("%s ",maxs[i].c_str());
     }
     printf("%02d:%02d:%02d",longest/,longest%/,longest%%);
 }

注意点：需要两个排序函数，只根据题目要求的排序函数不够用，每次要从头遍历就会超时。注意到题目里特别给出note，查询按时间前后来，因此考虑第二个用时间排序。把所有有效记录再保存到一个vector中，对其进行时间排序，针对每一次查询，不需要从头开始，只要记录上一次查询到的位置，继续查询即可。每进入一次计数加1，出去减1，由于保证了所有记录都是有效的，直接输出计数即为答案。