Dijkstras Algorithm

| Example Program Dijkstras Algorithm Computing single source shortest paths using Dijkstra algorithm. File "graph_algo_path_dijkstra.cpp" A tutorial about the dijkstra's algorithm, once using an external map and once using an internal map.
1 | #include <iostream>
2 | #include <seqan/graph_algorithms.h>
3 |
4 | using namespace seqan;
5 |
6 | int main() {
7 | typedef Graph<Directed<> > TGraph;
8 | typedef VertexDescriptor<TGraph>::Type TVertexDescriptor;
9 | typedef EdgeDescriptor<TGraph>::Type TEdgeDescriptor;
10 | typedef Size<TGraph>::Type TSize;
Graph creation: 10 directed edges (0,1), (0,3), ...
11 | TSize numEdges = 10;
12 | TVertexDescriptor edges[] = {0,1, 0,3, 1,2, 1,3, 2,4, 3,1, 3,2, 3,4, 4,0, 4,2};
13 | TGraph g;
14 | addEdges(g, edges, numEdges);
One external property map: Weight map
15 | unsigned int weights[] = {10, 5, 1, 2, 4, 3, 9, 2, 7, 6};
16 | String<unsigned int> weightMap;
17 | resizeEdgeMap(g,weightMap, weights);
Out-parameters: Predecessor and distance map
18 | String<unsigned int> predMap;
19 | String<unsigned int> distMap;
Dijkstra from vertex 0
20 | dijkstra(g,0,weightMap,predMap,distMap);
Console Output
21 | ::std::cout << "Single-Source Shortest Paths: " << ::std::endl;
22 | typedef Iterator<TGraph, VertexIterator>::Type TVertexIterator;
23 | TVertexIterator it(g);
24 | while(!atEnd(it)) {
25 | ::std::cout << "Path from 0 to " << getValue(it) << ": ";
26 | _printPath(g,predMap,(TVertexDescriptor) 0, getValue(it));
27 | ::std::cout << " (Distance: " << getProperty(distMap, getValue(it)) << ")" << ::std::endl;
28 | goNext(it);
29 | }
We can achieve the same thing using an internal map that is edge cargos.
30 | typedef unsigned int TEdgeCargo;
31 | typedef Directed<TEdgeCargo> TEdges;
32 | typedef Graph<TEdges> TCargoGraph;
Graph creation
33 | TCargoGraph cargo_g;
34 | addEdges(cargo_g, edges, numEdges);
One internal property map: Weight map
35 | InternalMap<TEdgeCargo> intMap;
36 | resizeEdgeMap(cargo_g,intMap, weights);
Out parameters of Dijkstra: Predecessor map and distance map
37 | clear(predMap);
38 | clear(distMap);
Dijkstra from vertex 0 using an internal map
39 | dijkstra(cargo_g,0,intMap,predMap,distMap);
Console Output
40 | ::std::cout << "Single-Source Shortest Paths: " << ::std::endl;
41 | typedef Iterator<TCargoGraph, VertexIterator>::Type TCargoVertexIterator;
42 | TCargoVertexIterator itC(cargo_g);
43 | while(!atEnd(itC)) {
44 | ::std::cout << "Path from 0 to " << getValue(itC) << ": ";
45 | _printPath(cargo_g,predMap,(TVertexDescriptor) 0, getValue(itC));
46 | ::std::cout << " (Distance: " << getProperty(distMap, getValue(itC)) << ")" << ::std::endl;
47 | goNext(itC);
48 | }
49 | return 0;
50 | }
See Graph, dijkstra SeqAn - Sequence Analysis Library - www.seqan.de

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