What is the optimal time complexity of solving Reconstruct Itinerary?

The optimized solution achieves a time complexity of O(n) by using sorting, mathematical shortcuts, or hash table lookups.

What is the auxiliary space complexity for Reconstruct Itinerary?

The space complexity is O(1) since we only use a minimal/constant amount of extra memory for tracking variables (or auxiliary space if dynamic structures are allocated).

What are the typical edge cases we must handle in Reconstruct Itinerary?

Key edge cases include empty collections, negative or large bounds causing integer overflow, arrays with only one element, or inputs where target criteria are not met.

How can we optimize the brute force approach for Reconstruct Itinerary?

Brute force methods often inspect all possible combinations. We optimize this by sorting the input list to enable binary search, or tracking processed items in a set to avoid redundant nested loop lookups.

Back to Practice Dashboard

Top 150 InterviewEasy

Reconstruct Itinerary

Learn how to solve the 'Reconstruct Itinerary' problem. This detailed resource details brute force and optimized approaches.

Mode Selected

Problem Statement

Easy

You are given a list of airline tickets where tickets[i] = [from_i, to_i] 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.

Write a function findItinerary(tickets: List[List[str]]) -> List[str].

Constraints

•1 <= len(tickets) <= 300
•tickets[i].length == 2
•from_i.length == 3
•to_i.length == 3
•from_i and to_i consist of uppercase English letters

Examples

Example 1

Input

tickets = [["MUC","LHR"],["JFK","MUC"],["SFO","SJC"],["LHR","SFO"]]

Output

["JFK","MUC","LHR","SFO","SJC"]

Explanation

The only valid itinerary is 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 lexically.

Need a Hint?

Represent graph node connections as an adjacency list/matrix, then use standard BFS or DFS graph traversal.

Edge Cases to Watch

Empty list or null input variables
Single item lists/arrays
Extremely large input bounds causing integer or stack overflow

Ready to Solve?

Open the problem in PyRun's browser-based Python editor. Your code runs fully offline — no server required.

Open in Editor