Is it cyclic?

Write a program that, given a directed graph, determines whether the
graph has any cycle or not.

Input

Input consists of several cases. Every case begins with the number of
vertices n and the number of arcs m of a graph G. Follow m pairs u, v,
indicating that there is an arc u → v in G, with u ≠ v. Assume
1 ≤ n ≤ 10⁴, 0 ≤ m ≤ 5n, and that for every pair of vertices u and v
there is at most one arc of the kind u → v. Vertices are numbered from 0
to n − 1.

Output

For every case, print “yes” or “no” depending on whether the graph has
any cycle or not.

Problem information

Author: Unknown
Translator: Enric Rodríguez

Generation: 2026-01-25T11:17:49.335Z

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