[3] 여행경로

vector<string> answer;
bool visited[100000001];
bool flag = false;
int cnt = 0;
 
void dfs(string cur, vector<vector<string>> tickets)
{
    if (cnt == tickets.size())
        flag = true;
 
    answer.push_back(cur);
 
    for (int i = 0; i < tickets.size(); i++) 
    {
        if (!visited[i] && 
            tickets[i][0] == cur) 
        {
            visited[i] = true;
            cnt++;
            dfs(tickets[i][1], tickets);
 
            if (!flag) 
            {
                answer.pop_back();
                visited[i] = false;
            }
        }
    }
}
 
vector<string> solution(vector<vector<string>> tickets) 
{
    sort(tickets.begin(), tickets.end());
    dfs("ICN", tickets);
    return answer;
}