Function is_cyclic_directed 

pub fn is_cyclic_directed<G>(g: G) -> bool
where
    G: IntoNodeIdentifiers + IntoNeighbors + Visitable,

Return true if the input directed graph contains a cycle.

This implementation is recursive; use toposort if an alternative is needed.

Arguments:

g: a directed graph.

Returns

true: if the input graph contains a cycle. false: otherwise.

Complexity

• Time complexity: O(|V| + |E|).
• Auxiliary space: O(|V|).

where |V| is the number of nodes and |E| is the number of edges.