1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536
use super::{GraphRef, IntoNodeIdentifiers, Reversed};
use super::{IntoNeighbors, IntoNeighborsDirected, VisitMap, Visitable};
use crate::Incoming;
use std::collections::VecDeque;
/// Visit nodes of a graph in a depth-first-search (DFS) emitting nodes in
/// preorder (when they are first discovered).
///
/// The traversal starts at a given node and only traverses nodes reachable
/// from it.
///
/// `Dfs` is not recursive.
///
/// `Dfs` does not itself borrow the graph, and because of this you can run
/// a traversal over a graph while still retaining mutable access to it, if you
/// use it like the following example:
///
/// ```
/// use petgraph::Graph;
/// use petgraph::visit::Dfs;
///
/// let mut graph = Graph::<_,()>::new();
/// let a = graph.add_node(0);
///
/// let mut dfs = Dfs::new(&graph, a);
/// while let Some(nx) = dfs.next(&graph) {
/// // we can access `graph` mutably here still
/// graph[nx] += 1;
/// }
///
/// assert_eq!(graph[a], 1);
/// ```
///
/// **Note:** The algorithm may not behave correctly if nodes are removed
/// during iteration. It may not necessarily visit added nodes or edges.
#[derive(Clone, Debug)]
pub struct Dfs<N, VM> {
/// The stack of nodes to visit
pub stack: Vec<N>,
/// The map of discovered nodes
pub discovered: VM,
}
impl<N, VM> Default for Dfs<N, VM>
where
VM: Default,
{
fn default() -> Self {
Dfs {
stack: Vec::new(),
discovered: VM::default(),
}
}
}
impl<N, VM> Dfs<N, VM>
where
N: Copy + PartialEq,
VM: VisitMap<N>,
{
/// Create a new **Dfs**, using the graph's visitor map, and put **start**
/// in the stack of nodes to visit.
pub fn new<G>(graph: G, start: N) -> Self
where
G: GraphRef + Visitable<NodeId = N, Map = VM>,
{
let mut dfs = Dfs::empty(graph);
dfs.move_to(start);
dfs
}
/// Create a `Dfs` from a vector and a visit map
pub fn from_parts(stack: Vec<N>, discovered: VM) -> Self {
Dfs { stack, discovered }
}
/// Clear the visit state
pub fn reset<G>(&mut self, graph: G)
where
G: GraphRef + Visitable<NodeId = N, Map = VM>,
{
graph.reset_map(&mut self.discovered);
self.stack.clear();
}
/// Create a new **Dfs** using the graph's visitor map, and no stack.
pub fn empty<G>(graph: G) -> Self
where
G: GraphRef + Visitable<NodeId = N, Map = VM>,
{
Dfs {
stack: Vec::new(),
discovered: graph.visit_map(),
}
}
/// Keep the discovered map, but clear the visit stack and restart
/// the dfs from a particular node.
pub fn move_to(&mut self, start: N) {
self.stack.clear();
self.stack.push(start);
}
/// Return the next node in the dfs, or **None** if the traversal is done.
pub fn next<G>(&mut self, graph: G) -> Option<N>
where
G: IntoNeighbors<NodeId = N>,
{
while let Some(node) = self.stack.pop() {
if self.discovered.visit(node) {
for succ in graph.neighbors(node) {
if !self.discovered.is_visited(&succ) {
self.stack.push(succ);
}
}
return Some(node);
}
}
None
}
}
/// Visit nodes in a depth-first-search (DFS) emitting nodes in postorder
/// (each node after all its descendants have been emitted).
///
/// `DfsPostOrder` is not recursive.
///
/// The traversal starts at a given node and only traverses nodes reachable
/// from it.
#[derive(Clone, Debug)]
pub struct DfsPostOrder<N, VM> {
/// The stack of nodes to visit
pub stack: Vec<N>,
/// The map of discovered nodes
pub discovered: VM,
/// The map of finished nodes
pub finished: VM,
}
impl<N, VM> Default for DfsPostOrder<N, VM>
where
VM: Default,
{
fn default() -> Self {
DfsPostOrder {
stack: Vec::new(),
discovered: VM::default(),
finished: VM::default(),
}
}
}
impl<N, VM> DfsPostOrder<N, VM>
where
N: Copy + PartialEq,
VM: VisitMap<N>,
{
/// Create a new `DfsPostOrder` using the graph's visitor map, and put
/// `start` in the stack of nodes to visit.
pub fn new<G>(graph: G, start: N) -> Self
where
G: GraphRef + Visitable<NodeId = N, Map = VM>,
{
let mut dfs = Self::empty(graph);
dfs.move_to(start);
dfs
}
/// Create a new `DfsPostOrder` using the graph's visitor map, and no stack.
pub fn empty<G>(graph: G) -> Self
where
G: GraphRef + Visitable<NodeId = N, Map = VM>,
{
DfsPostOrder {
stack: Vec::new(),
discovered: graph.visit_map(),
finished: graph.visit_map(),
}
}
/// Clear the visit state
pub fn reset<G>(&mut self, graph: G)
where
G: GraphRef + Visitable<NodeId = N, Map = VM>,
{
graph.reset_map(&mut self.discovered);
graph.reset_map(&mut self.finished);
self.stack.clear();
}
/// Keep the discovered and finished map, but clear the visit stack and restart
/// the dfs from a particular node.
pub fn move_to(&mut self, start: N) {
self.stack.clear();
self.stack.push(start);
}
/// Return the next node in the traversal, or `None` if the traversal is done.
pub fn next<G>(&mut self, graph: G) -> Option<N>
where
G: IntoNeighbors<NodeId = N>,
{
while let Some(&nx) = self.stack.last() {
if self.discovered.visit(nx) {
// First time visiting `nx`: Push neighbors, don't pop `nx`
for succ in graph.neighbors(nx) {
if !self.discovered.is_visited(&succ) {
self.stack.push(succ);
}
}
} else {
self.stack.pop();
if self.finished.visit(nx) {
// Second time: All reachable nodes must have been finished
return Some(nx);
}
}
}
None
}
}
/// A breadth first search (BFS) of a graph.
///
/// The traversal starts at a given node and only traverses nodes reachable
/// from it.
///
/// `Bfs` is not recursive.
///
/// `Bfs` does not itself borrow the graph, and because of this you can run
/// a traversal over a graph while still retaining mutable access to it, if you
/// use it like the following example:
///
/// ```
/// use petgraph::Graph;
/// use petgraph::visit::Bfs;
///
/// let mut graph = Graph::<_,()>::new();
/// let a = graph.add_node(0);
///
/// let mut bfs = Bfs::new(&graph, a);
/// while let Some(nx) = bfs.next(&graph) {
/// // we can access `graph` mutably here still
/// graph[nx] += 1;
/// }
///
/// assert_eq!(graph[a], 1);
/// ```
///
/// **Note:** The algorithm may not behave correctly if nodes are removed
/// during iteration. It may not necessarily visit added nodes or edges.
#[derive(Clone)]
pub struct Bfs<N, VM> {
/// The queue of nodes to visit
pub stack: VecDeque<N>,
/// The map of discovered nodes
pub discovered: VM,
}
impl<N, VM> Default for Bfs<N, VM>
where
VM: Default,
{
fn default() -> Self {
Bfs {
stack: VecDeque::new(),
discovered: VM::default(),
}
}
}
impl<N, VM> Bfs<N, VM>
where
N: Copy + PartialEq,
VM: VisitMap<N>,
{
/// Create a new **Bfs**, using the graph's visitor map, and put **start**
/// in the stack of nodes to visit.
pub fn new<G>(graph: G, start: N) -> Self
where
G: GraphRef + Visitable<NodeId = N, Map = VM>,
{
let mut discovered = graph.visit_map();
discovered.visit(start);
let mut stack = VecDeque::new();
stack.push_front(start);
Bfs { stack, discovered }
}
/// Return the next node in the bfs, or **None** if the traversal is done.
pub fn next<G>(&mut self, graph: G) -> Option<N>
where
G: IntoNeighbors<NodeId = N>,
{
if let Some(node) = self.stack.pop_front() {
for succ in graph.neighbors(node) {
if self.discovered.visit(succ) {
self.stack.push_back(succ);
}
}
return Some(node);
}
None
}
}
/// A topological order traversal for a graph.
///
/// **Note** that `Topo` only visits nodes that are not part of cycles,
/// i.e. nodes in a true DAG. Use other visitors like `DfsPostOrder` or
/// algorithms like kosaraju_scc to handle graphs with possible cycles.
#[derive(Clone)]
pub struct Topo<N, VM> {
tovisit: Vec<N>,
ordered: VM,
}
impl<N, VM> Default for Topo<N, VM>
where
VM: Default,
{
fn default() -> Self {
Topo {
tovisit: Vec::new(),
ordered: VM::default(),
}
}
}
impl<N, VM> Topo<N, VM>
where
N: Copy + PartialEq,
VM: VisitMap<N>,
{
/// Create a new `Topo`, using the graph's visitor map, and put all
/// initial nodes in the to visit list.
pub fn new<G>(graph: G) -> Self
where
G: IntoNodeIdentifiers + IntoNeighborsDirected + Visitable<NodeId = N, Map = VM>,
{
let mut topo = Self::empty(graph);
topo.extend_with_initials(graph);
topo
}
/// Create a new `Topo` with initial nodes.
///
/// Nodes with incoming edges are ignored.
pub fn with_initials<G, I>(graph: G, initials: I) -> Self
where
G: IntoNeighborsDirected + Visitable<NodeId = N, Map = VM>,
I: IntoIterator<Item = N>,
{
Topo {
tovisit: initials
.into_iter()
.filter(|&n| graph.neighbors_directed(n, Incoming).next().is_none())
.collect(),
ordered: graph.visit_map(),
}
}
fn extend_with_initials<G>(&mut self, g: G)
where
G: IntoNodeIdentifiers + IntoNeighborsDirected<NodeId = N>,
{
// find all initial nodes (nodes without incoming edges)
self.tovisit.extend(
g.node_identifiers()
.filter(move |&a| g.neighbors_directed(a, Incoming).next().is_none()),
);
}
/* Private until it has a use */
/// Create a new `Topo`, using the graph's visitor map with *no* starting
/// index specified.
fn empty<G>(graph: G) -> Self
where
G: GraphRef + Visitable<NodeId = N, Map = VM>,
{
Topo {
ordered: graph.visit_map(),
tovisit: Vec::new(),
}
}
/// Clear visited state, and put all initial nodes in the to visit list.
pub fn reset<G>(&mut self, graph: G)
where
G: IntoNodeIdentifiers + IntoNeighborsDirected + Visitable<NodeId = N, Map = VM>,
{
graph.reset_map(&mut self.ordered);
self.tovisit.clear();
self.extend_with_initials(graph);
}
/// Return the next node in the current topological order traversal, or
/// `None` if the traversal is at the end.
///
/// *Note:* The graph may not have a complete topological order, and the only
/// way to know is to run the whole traversal and make sure it visits every node.
pub fn next<G>(&mut self, g: G) -> Option<N>
where
G: IntoNeighborsDirected + Visitable<NodeId = N, Map = VM>,
{
// Take an unvisited element and find which of its neighbors are next
while let Some(nix) = self.tovisit.pop() {
if self.ordered.is_visited(&nix) {
continue;
}
self.ordered.visit(nix);
for neigh in g.neighbors(nix) {
// Look at each neighbor, and those that only have incoming edges
// from the already ordered list, they are the next to visit.
if Reversed(g)
.neighbors(neigh)
.all(|b| self.ordered.is_visited(&b))
{
self.tovisit.push(neigh);
}
}
return Some(nix);
}
None
}
}
/// A walker is a traversal state, but where part of the traversal
/// information is supplied manually to each next call.
///
/// This for example allows graph traversals that don't hold a borrow of the
/// graph they are traversing.
pub trait Walker<Context> {
type Item;
/// Advance to the next item
fn walk_next(&mut self, context: Context) -> Option<Self::Item>;
/// Create an iterator out of the walker and given `context`.
fn iter(self, context: Context) -> WalkerIter<Self, Context>
where
Self: Sized,
Context: Clone,
{
WalkerIter {
walker: self,
context,
}
}
}
/// A walker and its context wrapped into an iterator.
#[derive(Clone, Debug)]
pub struct WalkerIter<W, C> {
walker: W,
context: C,
}
impl<W, C> WalkerIter<W, C>
where
W: Walker<C>,
C: Clone,
{
pub fn context(&self) -> C {
self.context.clone()
}
pub fn inner_ref(&self) -> &W {
&self.walker
}
pub fn inner_mut(&mut self) -> &mut W {
&mut self.walker
}
}
impl<W, C> Iterator for WalkerIter<W, C>
where
W: Walker<C>,
C: Clone,
{
type Item = W::Item;
fn next(&mut self) -> Option<Self::Item> {
self.walker.walk_next(self.context.clone())
}
}
impl<'a, C, W: ?Sized> Walker<C> for &'a mut W
where
W: Walker<C>,
{
type Item = W::Item;
fn walk_next(&mut self, context: C) -> Option<Self::Item> {
(**self).walk_next(context)
}
}
impl<G> Walker<G> for Dfs<G::NodeId, G::Map>
where
G: IntoNeighbors + Visitable,
{
type Item = G::NodeId;
fn walk_next(&mut self, context: G) -> Option<Self::Item> {
self.next(context)
}
}
impl<G> Walker<G> for DfsPostOrder<G::NodeId, G::Map>
where
G: IntoNeighbors + Visitable,
{
type Item = G::NodeId;
fn walk_next(&mut self, context: G) -> Option<Self::Item> {
self.next(context)
}
}
impl<G> Walker<G> for Bfs<G::NodeId, G::Map>
where
G: IntoNeighbors + Visitable,
{
type Item = G::NodeId;
fn walk_next(&mut self, context: G) -> Option<Self::Item> {
self.next(context)
}
}
impl<G> Walker<G> for Topo<G::NodeId, G::Map>
where
G: IntoNeighborsDirected + Visitable,
{
type Item = G::NodeId;
fn walk_next(&mut self, context: G) -> Option<Self::Item> {
self.next(context)
}
}