# Reconstruct an Itinerary While Keeping an Unspecified Variant Explicit The interview report identifies LeetCode 332, **Reconstruct Itinerary**, and says that the interview used a slight variant. It does not record what changed. Use the canonical problem below as a preparation baseline, then explain what you must clarify before claiming that a solution handles the interview variant. ## Canonical Baseline You receive airline tickets as directed pairs `[from, to]`. Begin at `JFK`, use every ticket exactly once, and return the itinerary with the smallest lexical order among all valid itineraries. Duplicate tickets are distinct edges, and the canonical problem guarantees that at least one valid itinerary exists. Explain an algorithm, its correctness, its complexity, and why simply taking the smallest available destination without backtracking can fail. You may use an iterative or recursive form, but account for every ticket occurrence. ## Unknown Variant Boundary Before adapting the baseline, ask which detail changed. Possibilities to clarify include the starting airport, validity guarantee, lexical tie-break, requirement to use every ticket, duplicate-ticket behavior, desired output, or whether tickets arrive dynamically. Do not select one of these as the reported change without evidence. ### What a Strong Answer Covers - A directed multigraph that preserves duplicate tickets. - Hierholzer's algorithm with destinations consumed in lexical order. - Postorder route construction and reversal. - A check that the final route contains exactly `tickets.length + 1` airports. - A firm separation between canonical semantics and the missing variant. ### Follow-up Questions 1. Why does naive lexical walk selection risk getting stuck before all tickets are used? 2. How can reverse-sorted adjacency lists replace a min-heap? 3. Which variant changes would invalidate the canonical Eulerian-path solution?