69 lines
1.7 KiB
Go
69 lines
1.7 KiB
Go
|
// Copyright ©2014 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 topo
|
||
|
|
|
||
|
|
import (
|
||
|
|
"gonum.org/v1/gonum/graph"
|
||
|
|
"gonum.org/v1/gonum/graph/traverse"
|
||
|
|
)
|
||
|
|
|
||
|
|
// IsPathIn returns whether path is a path in g.
|
||
|
|
//
|
||
|
|
// As special cases, IsPathIn returns true for a zero length path or for
|
||
|
|
// a path of length 1 when the node in path exists in the graph.
|
||
|
|
func IsPathIn(g graph.Graph, path []graph.Node) bool {
|
||
|
|
switch len(path) {
|
||
|
|
case 0:
|
||
|
|
return true
|
||
|
|
case 1:
|
||
|
|
return g.Node(path[0].ID()) != nil
|
||
|
|
default:
|
||
|
|
var canReach func(uid, vid int64) bool
|
||
|
|
switch g := g.(type) {
|
||
|
|
case graph.Directed:
|
||
|
|
canReach = g.HasEdgeFromTo
|
||
|
|
default:
|
||
|
|
canReach = g.HasEdgeBetween
|
||
|
|
}
|
||
|
|
|
||
|
|
for i, u := range path[:len(path)-1] {
|
||
|
|
if !canReach(u.ID(), path[i+1].ID()) {
|
||
|
|
return false
|
||
|
|
}
|
||
|
|
}
|
||
|
|
return true
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
// PathExistsIn returns whether there is a path in g starting at from extending
|
||
|
|
// to to.
|
||
|
|
//
|
||
|
|
// PathExistsIn exists as a helper function. If many tests for path existence
|
||
|
|
// are being performed, other approaches will be more efficient.
|
||
|
|
func PathExistsIn(g graph.Graph, from, to graph.Node) bool {
|
||
|
|
var t traverse.BreadthFirst
|
||
|
|
return t.Walk(g, from, func(n graph.Node, _ int) bool { return n.ID() == to.ID() }) != nil
|
||
|
|
}
|
||
|
|
|
||
|
|
// ConnectedComponents returns the connected components of the undirected graph g.
|
||
|
|
func ConnectedComponents(g graph.Undirected) [][]graph.Node {
|
||
|
|
var (
|
||
|
|
w traverse.DepthFirst
|
||
|
|
c []graph.Node
|
||
|
|
cc [][]graph.Node
|
||
|
|
)
|
||
|
|
during := func(n graph.Node) {
|
||
|
|
c = append(c, n)
|
||
|
|
}
|
||
|
|
after := func() {
|
||
|
|
cc = append(cc, []graph.Node(nil))
|
||
|
|
cc[len(cc)-1] = append(cc[len(cc)-1], c...)
|
||
|
|
c = c[:0]
|
||
|
|
}
|
||
|
|
w.WalkAll(g, nil, after, during)
|
||
|
|
|
||
|
|
return cc
|
||
|
|
}
|