Code Room
CodingMediumcod-g1008
Subject Concurrency deadlock victimLevel Mid–Senior~25 minCommon in Concurrency · Algorithms & data structures interviewsIndustries Software development, Technology

Question

A database deadlock detector must pick a victim to abort. Given n transactions (0..n-1) and a list of wait-for edges [a, b] (a waits for b), find the smallest-numbered transaction that lies on at least one directed cycle (a deadlocked transaction). Aborting it is a candidate for breaking a deadlock. Return that transaction id, or -1 if there is no deadlock.

Implement
deadlock_victim(n: int, edges: list[list[int]]) → int
Examples
in[4,[[1,2],[2,3],[3,1]]]out1
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.

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.