Solution: Reconstruct Itinerary

Explore how to reconstruct an itinerary from airline tickets by applying Hierholzer's algorithm for Eulerian paths and depth-first search. Understand how to build and traverse a graph to find the correct flight order starting at JFK, prioritize lexical order, and solve this complex graph problem efficiently.

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Statement
Solution
- Time complexity
- Space complexity

Statement

Given a list of airline tickets where tickets[i] = [from_i, to_i] represent a departure airport and an arrival airport of a single flight, reconstruct the itinerary in the correct order and return it.

The person who owns these tickets always starts their journey from "JFK". Therefore, the itinerary must begin with "JFK". If there are multiple valid itineraries, you should prioritize the one with the smallest lexical ordeLexicographical order is a sorting arrangement similar to how words are arranged in a dictionary. It compares items character by character, based on their order in the alphabet or numerical value.r when considering a single string.

For example, the itinerary ["JFK", "EDU"] has a smaller lexical order than ["JFK", "EDX"].

Note: You may assume all tickets form at least one valid itinerary. You must use all the tickets exactly once.

Constraints:

$1 \leq$ tickets.length $\leq 300$
tickets[i].length $= 2$
from_i.length $= 3$
to_i.length $= 3$ ...