Changeset 1183:8f623d1833a7 in lemon0.x for doc/quicktour.dox
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 03/03/05 18:20:08 (19 years ago)
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doc/quicktour.dox
r1181 r1183 11 11 in telecommunication, computer networks, and other areas that I cannot 12 12 think of now. A very natural way of modelling these networks is by means 13 of a <b> graph</b> (we will always mean a directed graph by that). 13 of a <b> graph</b> (we will always mean a directed graph by that and say 14 <b> undirected graph </b> otherwise). 14 15 So if you want to write a program that works with 15 graphs then you might find it useful to use our library LEMON. 16 graphs then you might find it useful to use our library LEMON. LEMON 17 defines various graph concepts depending on what you want to do with the 18 graph: a very good description can be found in the page 19 about \ref graphs "graphs". 16 20 17 21 You will also want to assign data to the edges or nodes of the graph, for example a length or capacity function defined on the edges. You can do this in LEMON using so called \ref maps "maps". You can define a map on the nodes or on the edges of the graph and the value of the map (the range of the function) can be practically almost any type. Read more about maps \ref mapspage "here". 18 22 19 23 Some examples are the following (you will find links next to the code fragments that help to download full demo programs): … … 45 49 46 50 # The following code shows how to read a graph from a stream (e.g. a file). LEMON supports the DIMACS file format: it can read a graph instance from a file 47 in that format (find the documentation of the format on the web).51 in that format (find the documentation of the DIMECS file format on the web). 48 52 \code 49 53 Graph g; … … 51 55 readDimacs(f, g); 52 56 \endcode 53 One can also store network (graph+capacity on the edges) instances and other things in DIMACS format : to see the details read the documentation of the \ref dimacs.h "Dimacs file format reader".57 One can also store network (graph+capacity on the edges) instances and other things in DIMACS format and use these in LEMON: to see the details read the documentation of the \ref dimacs.h "Dimacs file format reader". 54 58 55 59 … … 58 62 usually solved using Dijkstra's algorithm. A utility 59 63 that solves this is the \ref lemon::Dijkstra "LEMON Dijkstra class". 60 A simple program using the \ref lemon::Dijkstra "LEMON Dijkstra class" is 61 as follows (we do not include the part that instantiates the graph and the length function): 64 The following code is a simple program using the \ref lemon::Dijkstra "LEMON 65 Dijkstra class" and it also shows how to define a map on the edges (the length 66 function): 62 67 63 68 \code 64 typedef Graph::EdgeMap<int> LengthMap; 65 Graph G; 66 Node s, t; 67 LengthMap cap(G); 68 ... 69 Dijkstra<Graph, LengthMap> 70 dijkstra_test(G, cap); 71 dijkstra_test.run(s); 69 70 typedef ListGraph Graph; 71 typedef Graph::Node Node; 72 typedef Graph::Edge Edge; 73 typedef Graph::EdgeMap<int> LengthMap; 74 75 Graph g; 76 77 //An example from Ahuja's book 78 79 Node s=g.addNode(); 80 Node v2=g.addNode(); 81 Node v3=g.addNode(); 82 Node v4=g.addNode(); 83 Node v5=g.addNode(); 84 Node t=g.addNode(); 85 86 Edge s_v2=g.addEdge(s, v2); 87 Edge s_v3=g.addEdge(s, v3); 88 Edge v2_v4=g.addEdge(v2, v4); 89 Edge v2_v5=g.addEdge(v2, v5); 90 Edge v3_v5=g.addEdge(v3, v5); 91 Edge v4_t=g.addEdge(v4, t); 92 Edge v5_t=g.addEdge(v5, t); 93 94 LengthMap len(g); 95 96 len.set(s_v2, 10); 97 len.set(s_v3, 10); 98 len.set(v2_v4, 5); 99 len.set(v2_v5, 8); 100 len.set(v3_v5, 5); 101 len.set(v4_t, 8); 102 len.set(v5_t, 8); 103 104 std::cout << "The id of s is " << g.id(s)<< ", the id of t is " << g.id(t)<<"."<<std::endl; 105 106 std::cout << "Dijkstra algorithm test..." << std::endl; 107 108 Dijkstra<Graph, LengthMap> dijkstra_test(g,len); 109 110 dijkstra_test.run(s); 111 112 113 std::cout << "The distance of node t from node s: " << dijkstra_test.dist(t)<<std::endl; 114 115 std::cout << "The shortest path from s to t goes through the following nodes (the first one is t, the last one is s): "<<std::endl; 116 117 for (Node v=t;v != s; v=dijkstra_test.predNode(v)){ 118 std::cout << g.id(v) << "<"; 119 } 120 std::cout << g.id(s) << std::endl; 72 121 \endcode 122 123 See the whole program in \file dijkstra_demo.cc. 124 125 The first part of the code is selfexplanatory: we build the graph and set the 126 length values of the edges. Then we instantiate a member of the Dijkstra class 127 and run the Dijkstra algorithm from node \c s. After this we read some of the 128 results. 129 You can do much more with the Dijkstra class, for example you can run it step 130 by step and gain full control of the execution. For a detailed description, see the documentation of the \ref lemon::Dijkstra "LEMON Dijkstra class". 131 73 132 74 133  If you want to design a network and want to minimize the total length … … 83 142 84 143 85 86 Some more detailed introduction can be obtained by following the links87 below:88 89 \ref graphs "Graph structures"90 play a central role in LEMON, so if you are new to the library,91 you probably should start \ref graphs "here".92 (You can also find that page along with others under93 <a class="el" href="pages.html"> Related Pages </a>.)94 95 If you are96 interested in data structures and algorithms in more details, then97 you should browse the reference manual part of the documentation.98 Section <a class="el" href="modules.html"> Modules </a>99 is a good starting point for this.100 144 */
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