"Leetcode" reconstruct itinerary (332)

1. Description

Given A list of airline tickets represented by pairs of departure and arrival airports [from, to] , reconstruct the itinerary in Order. All of the tickets belong to a man departs from JFK . Thus, the itinerary must begin with JFK .

Note:

1. If There is multiple valid itineraries, you should return the itinerary that have the smallest lexical order when read as A single string. For example, the itinerary have ["JFK", "LGA"] a smaller lexical order than ["JFK", "LGB"] .
2. All airports is represented by three capital letters (IATA code).
3. Assume all tickets form at least one valid itinerary.

Example 1:
tickets =[["MUC", "LHR"], ["JFK", "MUC"], ["SFO", "SJC"], ["LHR", "SFO"]]
Return ["JFK", "MUC", "LHR", "SFO", "SJC"] .

Example 2:
tickets =[["JFK","SFO"],["JFK","ATL"],["SFO","ATL"],["ATL","JFK"],["ATL","SFO"]]
Return ["JFK","ATL","JFK","SFO","ATL","SFO"] .
Another possible reconstruction is ["JFK","SFO","ATL","JFK","ATL","SFO"] . But it's larger in lexical order.

2. Answer

ImportJava.util.*; Public classSolution { PublicList<string>finditinerary (string[][] tickets) {List<String> result =NewArraylist<string>(); if(Tickets = =NULL|| Tickets.length = = 0){            returnresult; } Map<string, arraylist<string>> graph =NewHashmap<string, arraylist<string>>();  for(inti=0; i<tickets.length; i++){            if(!graph.containskey (tickets[i][0]) {ArrayList<String> adj =NewArraylist<string>(); Adj.add (tickets[i][1]); Graph.put (tickets[i][0], adj); }Else{ArrayList<String> Newadj = Graph.get (tickets[i][0]); Newadj.add (tickets[i][1]); Graph.put (tickets[i][0], Newadj); }        }         for(arraylist<string>a:graph.values ())        {Collections.sort (a); } Stack<String> stack =NewStack<string>(); Stack.push ("JFK");  while(!Stack.isempty ()) {             while(Graph.containskey (Stack.peek ()) &&!Graph.get (Stack.peek ()). IsEmpty ()) {Stack.push (Graph.get (Stack.peek ()). Remove (0)); } result.add (0, Stack.pop ()); }        returnresult; }}

"Leetcode" reconstruct itinerary (332)