Question
There are n tasks labeled 0..n-1 and a list of prerequisite pairs [a, b] meaning b must be finished before a. Each semester you may take any number of tasks whose prerequisites are all already finished. Return the minimum number of semesters needed to finish all tasks, or -1 if a cycle makes it impossible. With no prerequisites everything can be done in one semester.
min_semesters(n: int, prereqs: list[list[int]]) → int[4,[[1,0],[2,0],[3,1],[3,2]]]out3State 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.