[145] | 1 | /** |
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| 2 | * Sequential Version of Dijkstra's Algorithm |
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| 3 | */ |
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| 4 | |
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| 5 | import java.io.BufferedReader; |
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| 6 | import java.io.FileReader; |
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| 7 | import java.util.ArrayList; |
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| 8 | import java.util.Scanner; |
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| 9 | import java.util.TreeMap; |
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| 10 | import java.util.List; |
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| 11 | |
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| 12 | public class DijkstraColSeq { |
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| 13 | |
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| 14 | private final static Integer infinity = 2000; |
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| 15 | static int len = 0; |
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| 16 | |
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| 17 | /** |
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| 18 | * @param args |
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| 19 | * 0 - Filename where Vertices and Edges are stored |
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| 20 | * @param args |
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| 21 | * 1 - Name of the source vertex |
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| 22 | * @param args |
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| 23 | * 2 - Name of the destination vertex |
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| 24 | */ |
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| 25 | public static void main(String[] args) { |
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| 26 | String fileName = null; |
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| 27 | Vertex source = null; |
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| 28 | Vertex destination = null; |
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| 29 | if (args.length == 3) { |
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| 30 | fileName = args[0]; |
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| 31 | source = new Vertex(Integer.parseInt(args[1])); |
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| 32 | destination = new Vertex(Integer.parseInt(args[2])); |
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| 33 | } else { |
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| 34 | System.err.println("Invalid command-line arguements"); |
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| 35 | System.exit(0); |
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| 36 | } |
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| 37 | |
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| 38 | List<Vertex> vertices = new ArrayList<Vertex>(); |
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| 39 | ArrayList<Edge> edges = new ArrayList<Edge>(); |
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| 40 | try { |
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| 41 | BufferedReader in = new BufferedReader(new FileReader(fileName)); |
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| 42 | String line = in.readLine(); |
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| 43 | len = Integer.parseInt( line ); |
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| 44 | while ((line = in.readLine()) != null) { |
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| 45 | Scanner scan = new Scanner( line ); |
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| 46 | Vertex start = new Vertex( scan.nextInt() ); |
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| 47 | Vertex end = new Vertex( scan.nextInt() ); |
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| 48 | if( !vertices.contains( start ) ) vertices.add( start ); |
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| 49 | if( !vertices.contains( end ) ) vertices.add( end ); |
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| 50 | edges.add( new Edge( start, end, scan.nextInt() ) ); |
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| 51 | } |
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| 52 | in.close(); |
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| 53 | } catch( Exception e ) { |
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| 54 | e.printStackTrace(); |
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| 55 | } |
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| 56 | |
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| 57 | Graph g = new Graph(vertices, edges); |
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| 58 | |
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| 59 | //*** Dijkstra's Algorithm ***\\ |
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| 60 | TreeMap<Vertex, Integer> distFromSource = new TreeMap<Vertex, Integer>(); |
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| 61 | TreeMap<Vertex, Vertex> previousNode = new TreeMap<Vertex, Vertex>(); |
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| 62 | TreeMap<Vertex, Integer> unvisitedNodes = new TreeMap<Vertex, Integer>(); |
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| 63 | for( Vertex v : g.getVertices() ) { |
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| 64 | distFromSource.put( v, infinity ); |
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| 65 | previousNode.put( v, null ); |
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| 66 | unvisitedNodes.put( v, null ); |
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| 67 | } |
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| 68 | distFromSource.put(source, 0); |
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| 69 | |
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| 70 | for( Vertex v : unvisitedNodes.keySet() ) { |
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| 71 | Vertex currentNode = v; |
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| 72 | for( Vertex v2 : unvisitedNodes.keySet() ) { |
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| 73 | if( distFromSource.get( v2 ) < distFromSource.get( currentNode ) && unvisitedNodes.get( v2 ) == null ) |
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| 74 | currentNode = v2; |
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| 75 | } |
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| 76 | unvisitedNodes.put( currentNode, new Integer( 1 ) ); |
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| 77 | for( Edge e : g.getEdgesContaining( currentNode ) ) { |
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| 78 | int newDist = distFromSource.get( currentNode ) + e.getDistance(); |
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| 79 | Vertex otherVertex = e.getOtherVertex( currentNode ); |
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| 80 | if( newDist < distFromSource.get( otherVertex ) ) { |
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| 81 | distFromSource.put( otherVertex, newDist ); |
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| 82 | previousNode.put( otherVertex, currentNode ); |
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| 83 | } |
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| 84 | } |
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| 85 | } |
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| 86 | |
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| 87 | Vertex prev = previousNode.get( destination ); |
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| 88 | String output = "[" + destination.getName() + "]"; |
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| 89 | while( !source.equals( prev ) ) { |
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| 90 | output = "[" + prev.getName() + "] -> " + output; |
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| 91 | prev = previousNode.get( prev ); |
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| 92 | } |
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| 93 | output = "[" + source.getName() + "] -> " + output + " (Total Distance = " + distFromSource.get( destination ) + ")"; |
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| 94 | System.out.println( output ); |
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| 95 | } |
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| 96 | |
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| 97 | } |
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