CodingEasycod-g1196

Subject ArraysLevel Entry–Mid~12 minCommon in Algorithms & data structures interviewsIndustries Software development

Question

A returns desk scans package IDs as they arrive; an ID showing up more than once means a duplicate label. Given the scan log in order, return the first ID that appears exactly once in the whole log, or -1 if every ID repeats (or the log is empty). Example: [2, 3, 2, 4, 3] returns 4.

Implement

first_unique_scan(ids: list[int]) → int

Examples

in[[2,3,2,4,3]]out4

What a strong answer looks like

State your approach and its time/space complexity out loud before you optimize. Handle the edge cases (empty input, duplicates, overflow), and say why you chose this over the brute force. Green tests are the floor, not the grade.

Learn the concepts

Vibe coding: describe the solution in plain language (or narrate it) and the coach grades your approach. Generating runnable code from your description is coming next.

Run or narrate your approach, then ask the coach.