public class Solution
extends Object
332 - Reconstruct Itinerary\.
Hard
You are given a list of airline `tickets` where tickets[i] = [fromi, toi] represent the departure and the arrival airports of one flight. Reconstruct the itinerary in order and return it.
All of the tickets belong to a man who departs from `"JFK"`, thus, the itinerary must begin with `"JFK"`. If there are multiple valid itineraries, you should return the itinerary that has the smallest lexical order when read as a single string.
* For example, the itinerary `["JFK", "LGA"]` has a smaller lexical order than `["JFK", "LGB"]`.
You may assume all tickets form at least one valid itinerary. You must use all the tickets once and only once.
**Example 1:**
**Input:** tickets = \[\["MUC","LHR"],["JFK","MUC"],["SFO","SJC"],["LHR","SFO"]]
**Output:** ["JFK","MUC","LHR","SFO","SJC"]
**Example 2:**
**Input:** tickets = \[\["JFK","SFO"],["JFK","ATL"],["SFO","ATL"],["ATL","JFK"],["ATL","SFO"]]
**Output:** ["JFK","ATL","JFK","SFO","ATL","SFO"]
**Explanation:**
Another possible reconstruction is
["JFK","SFO","ATL","JFK","ATL","SFO"] but it is larger in lexical order.
**Constraints:**
* `1 <= tickets.length <= 300`
* `tickets[i].length == 2`
* fromi.length == 3
* toi.length == 3
* fromi and toi consist of uppercase English letters.
* fromi != toi