Reconstruct Itinerary

class Solution {
    List<String> res;
    Map<String, PriorityQueue<String>> nodes;
    public List<String> findItinerary(List<List<String>> tickets) {
        res = new ArrayList<>();
        nodes = new HashMap<>();
            
        for(List<String> ticket : tickets){
            nodes.putIfAbsent(ticket.get(0), new PriorityQueue<>());
            nodes.get(ticket.get(0)).add(ticket.get(1));
        }
        
        dfs("JFK");
        List<String> temp = new ArrayList<>();
        for(int i = res.size()-1; i >= 0; i--){
            temp.add(res.get(i));
        }
        return temp;
    }
    
    public void dfs(String current){
        PriorityQueue<String> arrivals = nodes.get(current);
        
        while (arrivals != null && !arrivals.isEmpty())
            dfs(arrivals.poll());
        res.add(current);
    }
}