Reconstruct Itinerary - Codey

Description Submissions Solution

Description Submissions Solution

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Solution

Updated: 2026-02-23

Idea

Find an Eulerian path that uses all tickets exactly once, with lexicographically smallest choice.

Approach

Hierholzer’s algorithm:

Build adjacency lists.
Use a min-heap for each origin to always take smallest next airport.
DFS: while outgoing edges exist, take smallest edge and recurse.
Append airport to result on backtrack; reverse at end.

Why it works

Hierholzer constructs an Eulerian trail by stitching cycles; using min-heaps ensures the lexicographically smallest valid itinerary.

Code

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Complexity

Time: O(E log E)

Space: O(E)

Solution

Updated: 2026-02-23

Idea

Find an Eulerian path that uses all tickets exactly once, with lexicographically smallest choice.

Approach

Hierholzer’s algorithm:

Build adjacency lists.
Use a min-heap for each origin to always take smallest next airport.
DFS: while outgoing edges exist, take smallest edge and recurse.
Append airport to result on backtrack; reverse at end.

Why it works

Hierholzer constructs an Eulerian trail by stitching cycles; using min-heaps ensures the lexicographically smallest valid itinerary.

Code

Loading...

Complexity

Time: O(E log E)

Space: O(E)