g0301_0400.s0332_reconstruct_itinerary.Solution Maven / Gradle / Ivy

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Java-based LeetCode algorithm problem solutions, regularly updated

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package g0301_0400.s0332_reconstruct_itinerary;

// #Hard #Depth_First_Search #Graph #Eulerian_Circuit
// #2022_07_10_Time_4_ms_(100.00%)_Space_43_MB_(91.20%)

import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.PriorityQueue;

public class Solution {
    public List findItinerary(List> tickets) {
        HashMap> map = new HashMap<>();
        LinkedList ans = new LinkedList<>();
        for (List ticket : tickets) {
            String src = ticket.get(0);
            String dest = ticket.get(1);
            PriorityQueue pq = map.getOrDefault(src, new PriorityQueue<>());
            pq.add(dest);
            map.put(src, pq);
        }
        dfs(map, "JFK", ans);
        return ans;
    }

    private void dfs(Map> map, String src, LinkedList ans) {
        PriorityQueue temp = map.get(src);
        while (temp != null && !temp.isEmpty()) {
            String nbr = temp.remove();
            dfs(map, nbr, ans);
        }
        ans.addFirst(src);
    }
}