/
traverse.go
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/
traverse.go
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// Copyright ©2015 The Gonum Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package traverse
import (
"gonum.org/v1/gonum/graph"
"gonum.org/v1/gonum/graph/internal/linear"
"gonum.org/v1/gonum/graph/internal/set"
)
var _ Graph = graph.Graph(nil)
// Graph is the subset of graph.Graph necessary for graph traversal.
type Graph interface {
// From returns all nodes that can be reached directly
// from the node with the given ID.
From(id int64) graph.Nodes
// Edge returns the edge from u to v, with IDs uid and vid,
// if such an edge exists and nil otherwise. The node v
// must be directly reachable from u as defined by
// the From method.
Edge(uid, vid int64) graph.Edge
}
// BreadthFirst implements stateful breadth-first graph traversal.
type BreadthFirst struct {
// Visit is called on all nodes on their first visit.
Visit func(graph.Node)
// Traverse is called on all edges that may be traversed
// during the walk. This includes edges that would hop to
// an already visited node.
//
// The value returned by Traverse determines whether
// an edge can be traversed during the walk.
Traverse func(graph.Edge) bool
queue linear.NodeQueue
visited set.Int64s
}
// Walk performs a breadth-first traversal of the graph g starting from the given node,
// depending on the Traverse field and the until parameter if they are non-nil.
// The traversal follows edges for which Traverse(edge) is true and returns the first node
// for which until(node, depth) is true. During the traversal, if the Visit field is
// non-nil, it is called with each node the first time it is visited.
func (b *BreadthFirst) Walk(g Graph, from graph.Node, until func(n graph.Node, d int) bool) graph.Node {
if b.visited == nil {
b.visited = make(set.Int64s)
}
b.queue.Enqueue(from)
if b.Visit != nil && !b.visited.Has(from.ID()) {
b.Visit(from)
}
b.visited.Add(from.ID())
var (
depth int
children int
untilNext = 1
)
for b.queue.Len() > 0 {
t := b.queue.Dequeue()
if until != nil && until(t, depth) {
return t
}
tid := t.ID()
to := g.From(tid)
for to.Next() {
n := to.Node()
nid := n.ID()
if b.Traverse != nil && !b.Traverse(g.Edge(tid, nid)) {
continue
}
if b.visited.Has(nid) {
continue
}
if b.Visit != nil {
b.Visit(n)
}
b.visited.Add(nid)
children++
b.queue.Enqueue(n)
}
if untilNext--; untilNext == 0 {
depth++
untilNext = children
children = 0
}
}
return nil
}
// WalkAll calls Walk for each unvisited node of the graph g using edges independent
// of their direction. The functions before and after are called prior to commencing
// and after completing each walk if they are non-nil respectively. The function
// during is called on each node as it is traversed.
func (b *BreadthFirst) WalkAll(g graph.Undirected, before, after func(), during func(graph.Node)) {
b.Reset()
nodes := g.Nodes()
for nodes.Next() {
from := nodes.Node()
if b.Visited(from) {
continue
}
if before != nil {
before()
}
b.Walk(g, from, func(n graph.Node, _ int) bool {
if during != nil {
during(n)
}
return false
})
if after != nil {
after()
}
}
}
// Visited returned whether the node n was visited during a traverse.
func (b *BreadthFirst) Visited(n graph.Node) bool {
return b.visited.Has(n.ID())
}
// Reset resets the state of the traverser for reuse.
func (b *BreadthFirst) Reset() {
b.queue.Reset()
b.visited = nil
}
// DepthFirst implements stateful depth-first graph traversal.
type DepthFirst struct {
// Visit is called on all nodes on their first visit.
Visit func(graph.Node)
// Traverse is called on all edges that may be traversed
// during the walk. This includes edges that would hop to
// an already visited node.
//
// The value returned by Traverse determines whether an
// edge can be traversed during the walk.
Traverse func(graph.Edge) bool
stack linear.NodeStack
visited set.Int64s
}
// Walk performs a depth-first traversal of the graph g starting from the given node,
// depending on the Traverse field and the until parameter if they are non-nil.
// The traversal follows edges for which Traverse(edge) is true and returns the first node
// for which until(node) is true. During the traversal, if the Visit field is non-nil, it
// is called with each node the first time it is visited.
func (d *DepthFirst) Walk(g Graph, from graph.Node, until func(graph.Node) bool) graph.Node {
if d.visited == nil {
d.visited = make(set.Int64s)
}
d.stack.Push(from)
for d.stack.Len() != 0 {
u := d.stack.Pop()
uid := u.ID()
if d.visited.Has(uid) {
continue
}
d.visited.Add(uid)
if d.Visit != nil {
d.Visit(u)
}
if until != nil && until(u) {
return u
}
to := g.From(uid)
for to.Next() {
v := to.Node()
vid := v.ID()
if d.Traverse != nil && !d.Traverse(g.Edge(uid, vid)) {
continue
}
d.stack.Push(v)
}
}
return nil
}
// WalkAll calls Walk for each unvisited node of the graph g using edges independent
// of their direction. The functions before and after are called prior to commencing
// and after completing each walk if they are non-nil respectively. The function
// during is called on each node as it is traversed.
func (d *DepthFirst) WalkAll(g graph.Undirected, before, after func(), during func(graph.Node)) {
d.Reset()
nodes := g.Nodes()
for nodes.Next() {
from := nodes.Node()
if d.Visited(from) {
continue
}
if before != nil {
before()
}
d.Walk(g, from, func(n graph.Node) bool {
if during != nil {
during(n)
}
return false
})
if after != nil {
after()
}
}
}
// Visited returned whether the node n was visited during a traverse.
func (d *DepthFirst) Visited(n graph.Node) bool {
return d.visited.Has(n.ID())
}
// Reset resets the state of the traverser for reuse.
func (d *DepthFirst) Reset() {
d.stack = d.stack[:0]
d.visited = nil
}