my code(85 WA):

#include <bits/stdc++.h>
using namespace std;
using LL = long long;
const LL keep_time = 86400000;
struct IP{
    int page_num;
    LL last_exit_time;
    string user_name;
    IP(){page_num = 0, user_name = "", last_exit_time = 0;}
};
struct User{
    string pwd;
    set<string> login_ip;
    User(){pwd = "", login_ip.clear();}
};
struct Submit_Result{
    string name, state;
    LL usedtime;
    Submit_Result(){name = "", state = "", usedtime = 0;}
    Submit_Result(string _name, string _state, LL _usedtime){
        name = _name, state = _state, usedtime = _usedtime;
    }
    bool operator<(const Submit_Result& a) const {
        if(state == "AC" && a.state != "AC") return 1;
        if(state != "AC" && a.state == "AC") return 0;
        return usedtime < a.usedtime;
    }
};
struct Ans{
    LL time, judge_time, tot_time;
    string state, name, question;
    Ans(LL _time, LL _judge_time, string _name, string _state, string _question){
        time = _time, judge_time = _judge_time, name = _name, state = _state, question = _question;
        tot_time = time + judge_time;
    }
    bool operator<(const Ans& a) const {
        return tot_time > a.tot_time;
    }
};
priority_queue<Ans> order_submit;
map<string, IP> ip_map;
map<string, User> user_map;
map<string, map<string, string>> user_State;
map<string, set<Submit_Result>> rank_table;
int n;
LL t, judgetime;
string ip, name, pwd, newpwd, question, state, command;
void print_submit(LL t){
    while(order_submit.size() && order_submit.top().tot_time <= t){
        auto i = order_submit.top();
        cout << "[" << i.tot_time << "] USER " << i.name << " " << i.state << " IN " << i.question << '\n';
        if(user_State[i.question][i.name] != "AC"){
            user_State[i.question][i.name] = i.state;
            rank_table[i.question].insert({i.name, i.state, i.time});
        }
        order_submit.pop();
    }
}
int main(){
    //freopen("oj.in", "r", stdin);
    //freopen("oj.out", "w", stdout);
    ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
    cin >> n;
    while(n --){
        cin >> t >> command >> ip;
        print_submit(t);
        if(command == "connect"){
            if(ip_map[ip].page_num == 0){
                cout << "[" << t << "] CONNECTED TO " << ip << '\n';
                if(t - ip_map[ip].last_exit_time <= keep_time)
                    user_map[ip_map[ip].user_name].login_ip.insert(ip);
                else ip_map[ip].user_name = "";
            }
            ++ ip_map[ip].page_num;
            continue;
        }
        /*if(ip_map[ip].page_num == 0){
            string ex;
            getline(cin, ex);
            continue;
        }*/
        if(command == "exit"){
            if(ip_map[ip].page_num == 1){
                if(ip_map[ip].user_name != "")
                user_map[ip_map[ip].user_name].login_ip.erase(ip);
                ip_map[ip].last_exit_time = t;
                cout << "[" << t << "] CONNECTION TO " << ip << " RELEASED\n";
            }
            -- ip_map[ip].page_num;
            continue;
        }
        if(command == "register"){
            cin >> name >> pwd;
            if(ip_map[ip].user_name != "")
                cout << "[" << t << "] NOT LOGGED OUT AT " << ip << '\n';
            else if(user_map[name].pwd != "")
                cout << "[" << t << "] USER " << name << " EXIST\n";
            else{
                cout << "[" << t << "] USER " << name << " REGISTERED\n";
                user_map[name].pwd = pwd;
            }
            continue;
        }
        if(command == "login"){
            cin >> name >> pwd;
            if(ip_map[ip].user_name != "")
                cout << "[" << t << "] NOT LOGGED OUT AT " << ip << '\n';
            else if(user_map[name].pwd == "")
                cout << "[" << t << "] USER " << name << " DO NOT EXIST\n";
            else if(user_map[name].pwd != pwd)
                cout << "[" << t << "] WRONG PASSWORD\n";
            else{
                cout << "[" << t << "] USER " << name << " LOGGED IN AT " << ip << '\n';
                ip_map[ip].user_name = name;
                user_map[name].login_ip.insert(ip);
            }
            continue;
        }
        if(ip_map[ip].user_name == ""){
            cout << "[" << t << "] NOT LOGGED IN AT " << ip << '\n';
            string ex;
            getline(cin, ex);
            continue;
        }
        if(command == "change"){
            cin >> pwd >> newpwd;
            if(user_map[ip_map[ip].user_name].pwd != pwd){
                cout << "[" << t << "] WRONG PASSWORD\n";
            }
            else{
                cout << "[" << t << "] PASSWORD CHANGED AT " << ip << '\n';
                user_map[ip_map[ip].user_name].pwd = newpwd;
                string kname = ip_map[ip].user_name;
                for(auto i : user_map[kname].login_ip){
                    ip_map[i].user_name = "";
                }
                user_map[kname].login_ip.clear();
            }
            continue;
        }
        if(command == "logout"){
            cout << "[" << t << "] USER " << ip_map[ip].user_name << " LOGGED OUT AT " << ip << '\n';
            user_map[ip_map[ip].user_name].login_ip.erase(ip);
            ip_map[ip].user_name = "";
            continue;
        }
        if(command == "submit"){
            cin >> question >> state >> judgetime;
            order_submit.push({t, judgetime, ip_map[ip].user_name, state, question});
            continue;
        }
        if(command == "rank"){
            cin >> name >> question;
            if(user_State[question][name] == "")
                cout << "[" << t << "] NO SUBMISSION OF USER " << name << " IN " << question << '\n';
            else{
                LL rank = 1, anstime;
                for(Submit_Result i : rank_table[question]){
                    if(i.name == name){
                        anstime = i.usedtime;
                        state = i.state;
                        break;
                    }
                    ++ rank;
                }
                cout << "[" << t << "] RANK OF USER " << name << " IN " << question << ":RANK=" << rank << ",STATE=" << state << ",TIME=" << anstime << '\n';
            }
            continue;
        }
    }
    print_submit(t);
    return 0;
}