PROG-T1004: Plate

#include <bits/stdc++.h>
using namespace std;

const int NR = 10;

map<int, int> mp;
list<queue<int>> lst;
list<queue<int>>::iterator idx[NR + 1];

int main(){

    int nRoom, nStu;
    scanf("%d%d", &nRoom, &nStu);
    for(int i = 1; i <= nRoom; ++i){
        idx[i] = lst.end();
    }
    for(int i = 1; i <= nStu; ++i){
        int room, id;
        scanf("%d%d", &room, &id);
        mp[id] = room;
    }
    while(true){
        char cmd;
        scanf(" %c", &cmd);
        if(cmd == 'X'){
            cout << "0\n";
            break;
        } else if(cmd == 'E'){
            int id;
            scanf("%d", &id);
            int room = mp[id];
            if(idx[room] == lst.end()){
                lst.emplace_back();
                idx[room] = (--lst.end());
            }
            idx[room] -> push(id);
        } else if(cmd == 'D'){
            if(lst.empty()){
                cout << "empty\n";
                continue;
            }
            int id = lst.front().front();
            cout << id << '\n';
            lst.front().pop();
            if(lst.front().empty()){
                idx[mp[id]] = lst.end();
                lst.pop_front();
            }
        }
    }

    return 0;
}