UVa 540 - Team Queue

// UVa 540 - Team Queue

import java.util.*;

public class Main {

    private static class TeamQueue<E, T> {

        private Map<E, T> memberToTeam = new HashMap<>();
        private Map<T, Queue<E>> teamToQueue = new HashMap<>();
        private Queue<T> teamOrder = new LinkedList<>();

        void addMember(E member, T teamIndex) {
            memberToTeam.put(member, teamIndex);
        }

        void enqueue(E member) {
            if (!memberToTeam.containsKey(member)) throw new IllegalArgumentException();
            T team = memberToTeam.get(member);

            if (!teamToQueue.containsKey(team)) {
                teamToQueue.put(team, new LinkedList<>());
            }
            if (teamToQueue.get(team).isEmpty()) {
                teamOrder.add(team);
            }
            teamToQueue.get(team).add(member);
        }

        E dequeue() {
            E member = teamToQueue.get(teamOrder.peek()).poll();
            while (!teamOrder.isEmpty() && teamToQueue.get(teamOrder.peek()).isEmpty())
                teamOrder.poll();
            return member;
        }

    }

    public static void main(String[] args) {
        int scenario = 0;
        try (Scanner scanner = new Scanner(System.in)) {

            while (true) {

                int numberOfTeams = scanner.nextInt();
                if (numberOfTeams == 0)
                    break;
                scenario++;
                System.out.println("Scenario #" + scenario);

                TeamQueue<Integer, Integer> teamQueue = new TeamQueue<>();

                for (int teamIndex = 0; teamIndex < numberOfTeams; teamIndex++) {
                    int teamSize = scanner.nextInt();
                    for (int j = 0; j < teamSize; j++) {
                        int member = scanner.nextInt();
                        teamQueue.addMember(member, teamIndex);
                    }
                }

                String instruction = scanner.next();
                while (!"STOP".equals(instruction)) {

                    if ("ENQUEUE".equals(instruction)) {
                        int member = scanner.nextInt();
                        teamQueue.enqueue(member);
                    } else {
                        System.out.println(teamQueue.dequeue());
                    }

                    instruction = scanner.next();
                }
                System.out.println();
            }
        }
    }
}