CodingMediumcod-g737

Subject Cycle detectionLevel Mid–Senior~25 minCommon in Algorithms & data structures interviewsIndustries Software development, IT services

Question

A build system has n targets (0..n-1) and `edges` `[a, b]` meaning target a depends on target b. A circular dependency makes the build impossible. Return the smallest-numbered node that participates in any dependency cycle, or -1 if the dependency graph is acyclic. A self-loop `[a, a]` counts as a cycle on node a.

Implement

find_cycle_node(n: int, edges: list[list[int]]) → int

Examples

in[4,[[0,1],[1,2],[2,0],[2,3]]]out0

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.