【算法导论-35】图算法JGraphT开源库介绍

Wiki

《算法导论》从22章开始图算法。但是Java JDK中没有Graph相关的库，自己实现的话可维护性较差。
JGraphT是一个开源的图理论数据结构和算法的开源库。可以在学习《算法导论》的同时学习该库，同时可以基于该库实现《算法导论》中相关图算法。

相关资料

JGraphT主页
JGraphT 源码GitHub主页
JGraphT jar包GitHub主页
JGraphT实现细节

简单实例

将“JGraphT jar包GitHub主页”的lib文件夹下的jgrapht-core-0.9.2.jar包添加项目工程中。
第一个实例时官方提供的简单有向图和无向图的例子。

import java.net.*;

import org.jgrapht.*;
import org.jgrapht.graph.*;


/**
 * A simple introduction to using JGraphT.
 *
 * @author Barak Naveh
 * @since Jul 27, 2003
 */
public final class HelloJGraphT
{
    private HelloJGraphT()
    {
    } // ensure non-instantiability.

    /**
     * The starting point for the demo.
     *
     * @param args ignored.
     */
    public static void main(String [] args)
    {
        UndirectedGraph<String, DefaultEdge> stringGraph = createStringGraph();

        // note undirected edges are printed as: {<v1>,<v2>}
        System.out.println(stringGraph);

        // create a graph based on URL objects
        DirectedGraph<URL, DefaultEdge> hrefGraph = createHrefGraph();

        // note directed edges are printed as: (<v1>,<v2>)
        System.out.println(hrefGraph);
    }

    /**
     * Creates a toy directed graph based on URL objects that represents link
     * structure.
     *
     * @return a graph based on URL objects.
     */
    private static DirectedGraph<URL, DefaultEdge> createHrefGraph()
    {
        DirectedGraph<URL, DefaultEdge> g =
                new DefaultDirectedGraph<>(DefaultEdge.class);

        try {
            URL amazon = new URL("http://www.amazon.com");
            URL yahoo = new URL("http://www.yahoo.com");
            URL ebay = new URL("http://www.ebay.com");

            // add the vertices
            g.addVertex(amazon);
            g.addVertex(yahoo);
            g.addVertex(ebay);

            // add edges to create linking structure
            g.addEdge(yahoo, amazon);
            g.addEdge(yahoo, ebay);
        } catch (MalformedURLException e) {
            e.printStackTrace();
        }

        return g;
    }

    /**
     * Create a toy graph based on String objects.
     *
     * @return a graph based on String objects.
     */
    private static UndirectedGraph<String, DefaultEdge> createStringGraph()
    {
        UndirectedGraph<String, DefaultEdge> g =
                new SimpleGraph<>(DefaultEdge.class);

        String v1 = "v1";
        String v2 = "v2";
        String v3 = "v3";
        String v4 = "v4";

        // add the vertices
        g.addVertex(v1);
        g.addVertex(v2);
        g.addVertex(v3);
        g.addVertex(v4);

        // add edges to create a circuit
        g.addEdge(v1, v2);
        g.addEdge(v2, v3);
        g.addEdge(v3, v4);
        g.addEdge(v4, v1);

        return g;
    }
}
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输出：

([v1, v2, v3, v4], [{v1,v2}, {v2,v3}, {v3,v4}, {v4,v1}])
([http://www.amazon.com, http://www.yahoo.com, http://www.ebay.com], [(http://www.yahoo.com,http://www.amazon.com), (http://www.yahoo.com,http://www.ebay.com)])
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