LeetCode : 332. Reconstruct Itinerary

[congr]

https://leetcode.com/problems/reconstruct-itinerary/

[congr]

O(NLogN), where N is the number of tickets.

class Solution {
    public List<String> findItinerary(String[][] tickets) {
        map = new HashMap();
        list = new ArrayList();

        for (String[] t: tickets) 
            map.computeIfAbsent(t[0], k -> new PriorityQueue()).add(t[1]); // !!!

        dfs("JFK");
        return list;        
    }

    Map<String, PriorityQueue<String>> map;
    List<String> list;

    void dfs (String here) {
        while (map.containsKey(here) && !map.get(here).isEmpty()) 
            dfs(map.get(here).remove());

        list.add(0, here); // route
    }
}