graph/path: add nodes to shortest path tree lazily
MODIFY
graph/path/a_star.go
graph/path/a_star.go
@@ -9,6 +9,7 @@ import (
"gonum.org/v1/gonum/graph"
"gonum.org/v1/gonum/graph/internal/set"
+ "gonum.org/v1/gonum/graph/traverse"
)
// AStar finds the A*-shortest path from s to t in g using the heuristic h. The path and
@@ -23,10 +24,12 @@ import (
// If h is nil, AStar will use the g.HeuristicCost method if g implements HeuristicCoster,
// falling back to NullHeuristic otherwise. If the graph does not implement Weighted,
// UniformCost is used. AStar will panic if g has an A*-reachable negative edge weight.
-func AStar(s, t graph.Node, g graph.Graph, h Heuristic) (path Shortest, expanded int) {
+func AStar(s, t graph.Node, g traverse.Graph, h Heuristic) (path Shortest, expanded int) {
+ if g, ok := g.(graph.Graph); ok {
if g.Node(s.ID()) == nil || g.Node(t.ID()) == nil {
return Shortest{from: s}, 0
}
+ }
var weight Weighting
if wg, ok := g.(Weighted); ok {
weight = wg.Weight
@@ -41,7 +44,7 @@ func AStar(s, t graph.Node, g graph.Graph, h Heuristic) (path Shortest, expanded
}
}
- path = newShortestFrom(s, graph.NodesOf(g.Nodes()))
+ path = newShortestFrom(s, []graph.Node{s, t})
tid := t.ID()
visited := make(set.Int64s)
@@ -64,14 +67,17 @@ func AStar(s, t graph.Node, g graph.Graph, h Heuristic) (path Shortest, expanded
if visited.Has(vid) {
continue
}
- j := path.indexOf[vid]
+ j, ok := path.indexOf[vid]
+ if !ok {
+ j = path.add(v)
+ }
w, ok := weight(u.node.ID(), vid)
if !ok {
- panic("A*: unexpected invalid weight")
+ panic("path: A* unexpected invalid weight")
}
if w < 0 {
- panic("A*: negative edge weight")
+ panic("path: A* negative edge weight")
}
g := u.gscore + w
if n, ok := open.node(vid); !ok {

graph/path: add nodes to shortest path tree lazily