332. Reconstruct Itinerary

class Solution {
    public List<String> findItinerary(List<List<String>> tickets) {
        Map<String, PriorityQueue<String>> graph = new HashMap<>();

        for(List<String> ticket : tickets){
            graph.computeIfAbsent(ticket.get(0), k -> new PriorityQueue<>()).add(ticket.get(1));
        }
        LinkedList<String> stack = new LinkedList<>();
        stack.add("JFK");
        LinkedList<String> itinerary = new LinkedList<>();

        while(!stack.isEmpty()){
            while(graph.getOrDefault(stack.peekLast(), new PriorityQueue<>()).size() > 0){
                stack.add(graph.get(stack.peekLast()).poll());
            }
            itinerary.addFirst(stack.pollLast());
        }
        return itinerary;
    }
}