blob: 261d4bc3cf47acd07cd7d1c99cac545ebd01335b [file] [log] [blame]
// 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 simple
import (
"fmt"
"gonum.org/v1/gonum/graph"
"gonum.org/v1/gonum/graph/internal/uid"
"gonum.org/v1/gonum/graph/iterator"
)
var (
ug *UndirectedGraph
_ graph.Graph = ug
_ graph.Undirected = ug
_ graph.NodeAdder = ug
_ graph.NodeRemover = ug
_ graph.EdgeAdder = ug
_ graph.EdgeRemover = ug
)
// UndirectedGraph implements a generalized undirected graph.
type UndirectedGraph struct {
nodes map[int64]graph.Node
edges map[int64]map[int64]graph.Edge
nodeIDs uid.Set
}
// NewUndirectedGraph returns an UndirectedGraph.
func NewUndirectedGraph() *UndirectedGraph {
return &UndirectedGraph{
nodes: make(map[int64]graph.Node),
edges: make(map[int64]map[int64]graph.Edge),
nodeIDs: uid.NewSet(),
}
}
// 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.edges[n.ID()] = make(map[int64]graph.Edge)
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.
func (g *UndirectedGraph) Edge(uid, vid int64) graph.Edge {
return g.EdgeBetween(uid, vid)
}
// EdgeBetween returns the edge between nodes x and y.
func (g *UndirectedGraph) EdgeBetween(xid, yid int64) graph.Edge {
edge, ok := g.edges[xid][yid]
if !ok {
return nil
}
return edge
}
// Edges returns all the edges in the graph.
func (g *UndirectedGraph) Edges() graph.Edges {
if len(g.edges) == 0 {
return graph.Empty
}
var edges []graph.Edge
seen := make(map[[2]int64]struct{})
for _, u := range g.edges {
for _, e := range u {
uid := e.From().ID()
vid := e.To().ID()
if _, ok := seen[[2]int64{uid, vid}]; ok {
continue
}
seen[[2]int64{uid, vid}] = struct{}{}
seen[[2]int64{vid, uid}] = struct{}{}
edges = append(edges, e)
}
}
if len(edges) == 0 {
return graph.Empty
}
return iterator.NewOrderedEdges(edges)
}
// From returns all nodes in g that can be reached directly from n.
func (g *UndirectedGraph) From(id int64) graph.Nodes {
if _, ok := g.nodes[id]; !ok {
return graph.Empty
}
nodes := make([]graph.Node, len(g.edges[id]))
i := 0
for from := range g.edges[id] {
nodes[i] = g.nodes[from]
i++
}
if len(nodes) == 0 {
return graph.Empty
}
return iterator.NewOrderedNodes(nodes)
}
// HasEdgeBetween returns whether an edge exists between nodes x and y.
func (g *UndirectedGraph) HasEdgeBetween(xid, yid int64) bool {
_, ok := g.edges[xid][yid]
return ok
}
// NewEdge returns a new Edge from the source to the destination node.
func (g *UndirectedGraph) NewEdge(from, to graph.Node) graph.Edge {
return &Edge{F: from, T: to}
}
// 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.
func (g *UndirectedGraph) Nodes() graph.Nodes {
if len(g.nodes) == 0 {
return graph.Empty
}
nodes := make([]graph.Node, len(g.nodes))
i := 0
for _, n := range g.nodes {
nodes[i] = n
i++
}
return iterator.NewOrderedNodes(nodes)
}
// RemoveEdge removes the edge with the given end IDs from the graph, leaving the terminal nodes.
// If the edge does not exist it is a no-op.
func (g *UndirectedGraph) RemoveEdge(fid, tid int64) {
if _, ok := g.nodes[fid]; !ok {
return
}
if _, ok := g.nodes[tid]; !ok {
return
}
delete(g.edges[fid], tid)
delete(g.edges[tid], fid)
}
// 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.edges[id] {
delete(g.edges[from], id)
}
delete(g.edges, id)
g.nodeIDs.Release(id)
}
// SetEdge adds e, an edge from one node to another. If the nodes do not exist, they are added
// and are set to the nodes of the edge otherwise.
// It will panic if the IDs of the e.From and e.To are equal.
func (g *UndirectedGraph) SetEdge(e graph.Edge) {
var (
from = e.From()
fid = from.ID()
to = e.To()
tid = to.ID()
)
if fid == tid {
panic("simple: adding self edge")
}
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
}
g.edges[fid][tid] = e
g.edges[tid][fid] = e
}