68 lines
1.5 KiB
Go
68 lines
1.5 KiB
Go
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// Copyright (c) 2016 Bitfury Group Limited
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// Distributed under the MIT software license, see the accompanying
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// file LICENSE or http://www.opensource.org/licenses/mit-license.php
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package graph
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import "math"
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func DijkstraPathWeight(g *Graph, source, target Vertex) (float64, error) {
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dist, _, err := dijkstra(g, source, target)
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if err != nil {
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return 0, err
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}
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if _, ok := dist[target]; !ok {
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return 0, PathNotFoundError
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}
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return dist[target], nil
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}
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func DijkstraPath(g *Graph, source, target Vertex) ([]Vertex, error) {
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_, parent, err := dijkstra(g, source, target)
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if err != nil {
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return nil, err
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}
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if _, ok := parent[target]; !ok {
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return nil, PathNotFoundError
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}
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path, err := Path(source, target, parent)
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if err != nil {
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return nil, err
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}
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return path, nil
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}
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func dijkstra(g *Graph, source, target Vertex) (map[Vertex]float64, map[Vertex]Vertex, error) {
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dist := make(map[Vertex]float64)
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colored := make(map[Vertex]bool)
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parent := make(map[Vertex]Vertex)
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dist[source] = 0
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for {
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bestDist := math.MaxFloat64
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var bestID Vertex
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for id, val := range dist {
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if val < bestDist && !colored[id] {
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bestDist = val
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bestID = id
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}
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}
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if bestID == target {
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break
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}
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colored[bestID] = true
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targets, err := g.GetNeighbors(bestID)
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if err != nil {
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return nil, nil, err
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}
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for id, multiedges := range targets {
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for _, edge := range multiedges {
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if have, ok := dist[id]; !ok || have > dist[bestID]+edge.Wgt {
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dist[id] = dist[bestID] + edge.Wgt
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parent[id] = bestID
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}
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}
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}
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}
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return dist, parent, nil
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}
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