/
grid.go
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/
grid.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 testgraphs
import (
"errors"
"fmt"
"math"
"gonum.org/v1/gonum/graph"
"gonum.org/v1/gonum/graph/iterator"
"gonum.org/v1/gonum/graph/simple"
)
const (
Closed = '*' // Closed is the closed grid node representation.
Open = '.' // Open is the open grid node repesentation.
Unknown = '?' // Unknown is the unknown grid node repesentation.
)
// Grid is a 2D grid planar undirected graph.
type Grid struct {
// AllowDiagonal specifies whether
// diagonally adjacent nodes can
// be connected by an edge.
AllowDiagonal bool
// UnitEdgeWeight specifies whether
// finite edge weights are returned as
// the unit length. Otherwise edge
// weights are the Euclidean distance
// between connected nodes.
UnitEdgeWeight bool
// AllVisible specifies whether
// non-open nodes are visible
// in calls to Nodes and HasNode.
AllVisible bool
open []bool
r, c int
}
// NewGrid returns an r by c grid with all positions
// set to the specified open state.
func NewGrid(r, c int, open bool) *Grid {
states := make([]bool, r*c)
if open {
for i := range states {
states[i] = true
}
}
return &Grid{
open: states,
r: r,
c: c,
}
}
// NewGridFrom returns a grid specified by the rows strings. All rows must
// be the same length and must only contain the Open or Closed characters,
// NewGridFrom will panic otherwise.
func NewGridFrom(rows ...string) *Grid {
if len(rows) == 0 {
return nil
}
for i, r := range rows[:len(rows)-1] {
if len(r) != len(rows[i+1]) {
panic("grid: unequal row lengths")
}
}
states := make([]bool, 0, len(rows)*len(rows[0]))
for _, r := range rows {
for _, b := range r {
switch b {
case Closed:
states = append(states, false)
case Open:
states = append(states, true)
default:
panic(fmt.Sprintf("grid: invalid state: %q", r))
}
}
}
return &Grid{
open: states,
r: len(rows),
c: len(rows[0]),
}
}
// Nodes returns all the open nodes in the grid if AllVisible is
// false, otherwise all nodes are returned.
func (g *Grid) Nodes() graph.Nodes {
var nodes []graph.Node
for id, ok := range g.open {
if ok || g.AllVisible {
nodes = append(nodes, simple.Node(id))
}
}
return iterator.NewOrderedNodes(nodes)
}
// Node returns the node with the given ID if it exists in the graph,
// and nil otherwise.
func (g *Grid) Node(id int64) graph.Node {
if g.has(id) {
return simple.Node(id)
}
return nil
}
// has returns whether id represents a node in the grid. The state of
// the AllVisible field determines whether a non-open node is present.
func (g *Grid) has(id int64) bool {
return 0 <= id && id < int64(len(g.open)) && (g.AllVisible || g.open[id])
}
// HasOpen returns whether n is an open node in the grid.
func (g *Grid) HasOpen(id int64) bool {
return 0 <= id && id < int64(len(g.open)) && g.open[id]
}
// Set sets the node at position (r, c) to the specified open state.
func (g *Grid) Set(r, c int, open bool) {
if r < 0 || r >= g.r {
panic("grid: illegal row index")
}
if c < 0 || c >= g.c {
panic("grid: illegal column index")
}
g.open[r*g.c+c] = open
}
// Dims returns the dimensions of the grid.
func (g *Grid) Dims() (r, c int) {
return g.r, g.c
}
// RowCol returns the row and column of the id. RowCol will panic if the
// node id is outside the range of the grid.
func (g *Grid) RowCol(id int64) (r, c int) {
if id < 0 || int64(len(g.open)) <= id {
panic("grid: illegal node id")
}
return int(id) / g.c, int(id) % g.c
}
// XY returns the cartesian coordinates of n. If n is not a node
// in the grid, (NaN, NaN) is returned.
func (g *Grid) XY(id int64) (x, y float64) {
if !g.has(id) {
return math.NaN(), math.NaN()
}
r, c := g.RowCol(id)
return float64(c), float64(r)
}
// NodeAt returns the node at (r, c). The returned node may be open or closed.
func (g *Grid) NodeAt(r, c int) graph.Node {
if r < 0 || r >= g.r || c < 0 || c >= g.c {
return nil
}
return simple.Node(r*g.c + c)
}
// From returns all the nodes reachable from u. Reachabilty requires that both
// ends of an edge must be open.
func (g *Grid) From(uid int64) graph.Nodes {
if !g.HasOpen(uid) {
return graph.Empty
}
nr, nc := g.RowCol(uid)
var to []graph.Node
for r := nr - 1; r <= nr+1; r++ {
for c := nc - 1; c <= nc+1; c++ {
if v := g.NodeAt(r, c); v != nil && g.HasEdgeBetween(uid, v.ID()) {
to = append(to, v)
}
}
}
if len(to) == 0 {
return graph.Empty
}
return iterator.NewOrderedNodes(to)
}
// HasEdgeBetween returns whether there is an edge between u and v.
func (g *Grid) HasEdgeBetween(uid, vid int64) bool {
if !g.HasOpen(uid) || !g.HasOpen(vid) || uid == vid {
return false
}
ur, uc := g.RowCol(uid)
vr, vc := g.RowCol(vid)
if abs(ur-vr) > 1 || abs(uc-vc) > 1 {
return false
}
return g.AllowDiagonal || ur == vr || uc == vc
}
func abs(i int) int {
if i < 0 {
return -i
}
return i
}
// Edge returns the edge between u and v.
func (g *Grid) Edge(uid, vid int64) graph.Edge {
return g.WeightedEdgeBetween(uid, vid)
}
// WeightedEdge returns the weighted edge between u and v.
func (g *Grid) WeightedEdge(uid, vid int64) graph.WeightedEdge {
return g.WeightedEdgeBetween(uid, vid)
}
// EdgeBetween returns the edge between u and v.
func (g *Grid) EdgeBetween(uid, vid int64) graph.Edge {
return g.WeightedEdgeBetween(uid, vid)
}
// WeightedEdgeBetween returns the weighted edge between u and v.
func (g *Grid) WeightedEdgeBetween(uid, vid int64) graph.WeightedEdge {
if g.HasEdgeBetween(uid, vid) {
if !g.AllowDiagonal || g.UnitEdgeWeight {
return simple.WeightedEdge{F: simple.Node(uid), T: simple.Node(vid), W: 1}
}
ux, uy := g.XY(uid)
vx, vy := g.XY(vid)
return simple.WeightedEdge{F: simple.Node(uid), T: simple.Node(vid), W: math.Hypot(ux-vx, uy-vy)}
}
return nil
}
// Weight returns the weight of the given edge.
func (g *Grid) Weight(xid, yid int64) (w float64, ok bool) {
if xid == yid {
return 0, true
}
if !g.HasEdgeBetween(xid, yid) {
return math.Inf(1), false
}
if e := g.EdgeBetween(xid, yid); e != nil {
if !g.AllowDiagonal || g.UnitEdgeWeight {
return 1, true
}
ux, uy := g.XY(e.From().ID())
vx, vy := g.XY(e.To().ID())
return math.Hypot(ux-vx, uy-vy), true
}
return math.Inf(1), true
}
// String returns a string representation of the grid.
func (g *Grid) String() string {
b, _ := g.Render(nil)
return string(b)
}
// Render returns a text representation of the graph
// with the given path included. If the path is not a path
// in the grid Render returns a non-nil error and the
// path up to that point.
func (g *Grid) Render(path []graph.Node) ([]byte, error) {
b := make([]byte, g.r*(g.c+1)-1)
for r := 0; r < g.r; r++ {
for c := 0; c < g.c; c++ {
if g.open[r*g.c+c] {
b[r*(g.c+1)+c] = Open
} else {
b[r*(g.c+1)+c] = Closed
}
}
if r < g.r-1 {
b[r*(g.c+1)+g.c] = '\n'
}
}
// We don't use topo.IsPathIn at the outset because we
// want to draw as much as possible before failing.
for i, n := range path {
id := n.ID()
if !g.has(id) || (i != 0 && !g.HasEdgeBetween(path[i-1].ID(), id)) {
if 0 <= id && id < int64(len(g.open)) {
r, c := g.RowCol(id)
b[r*(g.c+1)+c] = '!'
}
return b, errors.New("grid: not a path in graph")
}
r, c := g.RowCol(id)
switch i {
case len(path) - 1:
b[r*(g.c+1)+c] = 'G'
case 0:
b[r*(g.c+1)+c] = 'S'
default:
b[r*(g.c+1)+c] = 'o'
}
}
return b, nil
}