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undirected.go
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undirected.go
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// 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 multi
import (
"fmt"
"gonum.org/v1/gonum/graph"
"gonum.org/v1/gonum/graph/iterator"
"gonum.org/v1/gonum/graph/set/uid"
)
var (
ug *UndirectedGraph
_ graph.Graph = ug
_ graph.Undirected = ug
_ graph.Multigraph = ug
_ graph.UndirectedMultigraph = ug
_ graph.NodeAdder = ug
_ graph.NodeRemover = ug
_ graph.LineAdder = ug
_ graph.LineRemover = ug
)
// UndirectedGraph implements a generalized undirected graph.
type UndirectedGraph struct {
nodes map[int64]graph.Node
lines map[int64]map[int64]map[int64]graph.Line
nodeIDs *uid.Set
lineIDs map[int64]map[int64]*uid.Set
}
// NewUndirectedGraph returns an UndirectedGraph.
func NewUndirectedGraph() *UndirectedGraph {
return &UndirectedGraph{
nodes: make(map[int64]graph.Node),
lines: make(map[int64]map[int64]map[int64]graph.Line),
nodeIDs: uid.NewSet(),
lineIDs: make(map[int64]map[int64]*uid.Set),
}
}
// AddNode adds n to the graph. It panics if the added node ID matches an existing node ID.
func (g *UndirectedGraph) AddNode(n graph.Node) {
if _, exists := g.nodes[n.ID()]; exists {
panic(fmt.Sprintf("simple: node ID collision: %d", n.ID()))
}
g.nodes[n.ID()] = n
g.nodeIDs.Use(n.ID())
}
// Edge returns the edge from u to v if such an edge exists and nil otherwise.
// The node v must be directly reachable from u as defined by the From method.
// The returned graph.Edge is a multi.Edge if an edge exists.
func (g *UndirectedGraph) Edge(uid, vid int64) graph.Edge {
l := g.LinesBetween(uid, vid)
if l == graph.Empty {
return nil
}
return Edge{F: g.Node(uid), T: g.Node(vid), Lines: l}
}
// EdgeBetween returns the edge between nodes x and y.
func (g *UndirectedGraph) EdgeBetween(xid, yid int64) graph.Edge {
return g.Edge(xid, yid)
}
// Edges returns all the edges in the graph. Each edge in the returned slice
// is a multi.Edge.
//
// The returned graph.Edges is only valid until the next mutation of
// the receiver.
func (g *UndirectedGraph) Edges() graph.Edges {
if len(g.lines) == 0 {
return graph.Empty
}
var edges []graph.Edge
for xid, u := range g.lines {
for yid, lines := range u {
if yid < xid {
// Do not consider lines when the To node ID is
// before the From node ID. Both orientations
// are stored.
continue
}
if len(lines) == 0 {
continue
}
edges = append(edges, Edge{
F: g.Node(xid),
T: g.Node(yid),
Lines: iterator.NewLines(lines),
})
}
}
if len(edges) == 0 {
return graph.Empty
}
return iterator.NewOrderedEdges(edges)
}
// From returns all nodes in g that can be reached directly from n.
//
// The returned graph.Nodes is only valid until the next mutation of
// the receiver.
func (g *UndirectedGraph) From(id int64) graph.Nodes {
if len(g.lines[id]) == 0 {
return graph.Empty
}
return iterator.NewNodesByLines(g.nodes, g.lines[id])
}
// HasEdgeBetween returns whether an edge exists between nodes x and y.
func (g *UndirectedGraph) HasEdgeBetween(xid, yid int64) bool {
_, ok := g.lines[xid][yid]
return ok
}
// Lines returns the lines from u to v if such an edge exists and nil otherwise.
// The node v must be directly reachable from u as defined by the From method.
func (g *UndirectedGraph) Lines(uid, vid int64) graph.Lines {
return g.LinesBetween(uid, vid)
}
// LinesBetween returns the lines between nodes x and y.
func (g *UndirectedGraph) LinesBetween(xid, yid int64) graph.Lines {
if !g.HasEdgeBetween(xid, yid) {
return graph.Empty
}
var lines []graph.Line
for _, l := range g.lines[xid][yid] {
if l.From().ID() != xid {
l = l.ReversedLine()
}
lines = append(lines, l)
}
return iterator.NewOrderedLines(lines)
}
// NewLine returns a new Line from the source to the destination node.
// The returned Line will have a graph-unique ID.
// The Line's ID does not become valid in g until the Line is added to g.
func (g *UndirectedGraph) NewLine(from, to graph.Node) graph.Line {
xid := from.ID()
yid := to.ID()
if yid < xid {
xid, yid = yid, xid
}
var lineID int64
switch {
case g.lineIDs[xid] == nil:
uids := uid.NewSet()
lineID = uids.NewID()
g.lineIDs[xid] = map[int64]*uid.Set{yid: uids}
case g.lineIDs[xid][yid] == nil:
uids := uid.NewSet()
lineID = uids.NewID()
g.lineIDs[xid][yid] = uids
default:
lineID = g.lineIDs[xid][yid].NewID()
}
return Line{F: from, T: to, UID: lineID}
}
// NewNode returns a new unique Node to be added to g. The Node's ID does
// not become valid in g until the Node is added to g.
func (g *UndirectedGraph) NewNode() graph.Node {
if len(g.nodes) == 0 {
return Node(0)
}
if int64(len(g.nodes)) == uid.Max {
panic("simple: cannot allocate node: no slot")
}
return Node(g.nodeIDs.NewID())
}
// Node returns the node with the given ID if it exists in the graph,
// and nil otherwise.
func (g *UndirectedGraph) Node(id int64) graph.Node {
return g.nodes[id]
}
// Nodes returns all the nodes in the graph.
//
// The returned graph.Nodes is only valid until the next mutation of
// the receiver.
func (g *UndirectedGraph) Nodes() graph.Nodes {
if len(g.nodes) == 0 {
return graph.Empty
}
return iterator.NewNodes(g.nodes)
}
// NodeWithID returns a Node with the given ID if possible. If a graph.Node
// is returned that is not already in the graph NodeWithID will return true
// for new and the graph.Node must be added to the graph before use.
func (g *UndirectedGraph) NodeWithID(id int64) (n graph.Node, new bool) {
n, ok := g.nodes[id]
if ok {
return n, false
}
return Node(id), true
}
// RemoveLine removes the line with the given end point and line Ids from the graph, leaving
// the terminal nodes. If the line does not exist it is a no-op.
func (g *UndirectedGraph) RemoveLine(fid, tid, id int64) {
if _, ok := g.nodes[fid]; !ok {
return
}
if _, ok := g.nodes[tid]; !ok {
return
}
delete(g.lines[fid][tid], id)
if len(g.lines[fid][tid]) == 0 {
delete(g.lines[fid], tid)
}
delete(g.lines[tid][fid], id)
if len(g.lines[tid][fid]) == 0 {
delete(g.lines[tid], fid)
}
xid := fid
yid := tid
if yid < xid {
xid, yid = yid, xid
}
g.lineIDs[xid][yid].Release(id)
}
// RemoveNode removes the node with the given ID from the graph, as well as any edges attached
// to it. If the node is not in the graph it is a no-op.
func (g *UndirectedGraph) RemoveNode(id int64) {
if _, ok := g.nodes[id]; !ok {
return
}
delete(g.nodes, id)
for from := range g.lines[id] {
delete(g.lines[from], id)
}
delete(g.lines, id)
g.nodeIDs.Release(id)
}
// SetLine adds l, a line from one node to another. If the nodes do not exist, they are added
// and are set to the nodes of the line otherwise.
func (g *UndirectedGraph) SetLine(l graph.Line) {
var (
from = l.From()
fid = from.ID()
to = l.To()
tid = to.ID()
lid = l.ID()
)
if _, ok := g.nodes[fid]; !ok {
g.AddNode(from)
} else {
g.nodes[fid] = from
}
if _, ok := g.nodes[tid]; !ok {
g.AddNode(to)
} else {
g.nodes[tid] = to
}
switch {
case g.lines[fid] == nil:
g.lines[fid] = map[int64]map[int64]graph.Line{tid: {lid: l}}
case g.lines[fid][tid] == nil:
g.lines[fid][tid] = map[int64]graph.Line{lid: l}
default:
g.lines[fid][tid][lid] = l
}
switch {
case g.lines[tid] == nil:
g.lines[tid] = map[int64]map[int64]graph.Line{fid: {lid: l}}
case g.lines[tid][fid] == nil:
g.lines[tid][fid] = map[int64]graph.Line{lid: l}
default:
g.lines[tid][fid][lid] = l
}
xid := fid
yid := tid
if yid < xid {
xid, yid = yid, xid
}
switch {
case g.lineIDs[xid] == nil:
uids := uid.NewSet()
g.lineIDs[xid] = map[int64]*uid.Set{yid: uids}
case g.lineIDs[xid][yid] == nil:
uids := uid.NewSet()
g.lineIDs[xid][yid] = uids
}
g.lineIDs[xid][yid].Use(lid)
}