public string[] solution(string[,] tickets)
{
List <string> answer = new List <string>();
List <Airport> tmp = new List <Airport>();
for (int i = 0; i < tickets.GetLength(0); i++)
{
tmp.Add(new Airport(tickets[i, 0], tickets[i, 1]));
}
tmp = new List <Airport>(tmp.OrderBy(x => x.dep).ThenBy(b => b.des));
for (int i = 0; i < tmp.Count; i++)
{
tickets[i, 0] = tmp[i].dep;
tickets[i, 1] = tmp[i].des;
}
visit = new bool[tickets.Length];
Visit.Enqueue("ICN");
Dfs("ICN", tickets, 0);
return(Visit.ToArray());
}