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use crate::set::AssocSet;
/// Interfaces to run DFS on a graph.
pub trait DFSGraph {
/// [`Self::Identifier`] is used to get/access nodes in user-defined graph data structure.
/// For example, if the graph nodes are stored in a [`std::vec::Vec`], [`core::primitive::usize`] (the vector index)
/// can be a good candidate.
type Identifier: Clone + PartialEq + Eq + Copy;
/// [`Self::Set`] is used to store some temporary data associated with the nodes. For example,
/// in the case of using vector index mentioned above, [`std::vec::Vec`] itself can be a good choice for
/// this association set. See [`AssocSet`] for requirements of the data structure.
type Set<Y>: AssocSet<Self::Identifier, Y>
where
Y: Clone + Default;
/// [`Self::SuccessorIter`] iterates over the outgoing edges of a single node. It is used in
/// [`Self::outgoing_edges`].
type SuccessorIter<'a>: Iterator<Item = Self::Identifier>
where
Self: 'a;
/// Create a default initialized [`Self::Set`]
fn create_set<Y>(&self) -> Self::Set<Y>
where
Y: Clone + Default;
/// Get an iterator over the outgoing_edges of the given node.
fn outgoing_edges(&self, id: Self::Identifier) -> Self::SuccessorIter<'_>;
/// This method is automatically derived. It gives the post order sequence of the graph.
fn post_order_sequence(&self, root: Self::Identifier) -> Vec<Self::Identifier> {
let mut stack = Vec::new();
let mut visited = self.create_set();
let mut visitor = |i| stack.push(i);
self.post_order_visit(&mut visited, root, &mut visitor);
stack
}
/// This method is automatically derived. It visits the graph in post order.
fn post_order_visit<F>(&self, set: &mut Self::Set<bool>, current: Self::Identifier, f: &mut F)
where
F: FnMut(Self::Identifier),
{
if set.get(current) {
return;
}
set.set(current, true);
for i in self.outgoing_edges(current) {
self.post_order_visit(set, i, f);
}
f(current);
}
}