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NavyDNavyD
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使用git管理my-lib
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‎pom.xml‎

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<project xmlns="http://maven.apache.org/POM/4.0.0"
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xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<modelVersion>4.0.0</modelVersion>
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<groupId>cn.navyd</groupId>
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<artifactId>my-lib</artifactId>
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<version>1.0-SNAPSHOT</version>
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<packaging>jar</packaging>
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<name>my-lib</name>
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<url>http://maven.apache.org</url>
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<properties>
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<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
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<maven.compiler.source>1.8</maven.compiler.source>
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<maven.compiler.target>1.8</maven.compiler.target>
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<junit.version>4.12</junit.version>
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<lombok.version>1.18.0</lombok.version>
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<slf4j.version>1.7.25</slf4j.version>
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<logback.version>1.2.3</logback.version>
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</properties>
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<dependencies>
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<dependency>
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<groupId>junit</groupId>
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<artifactId>junit</artifactId>
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<version>${junit.version}</version>
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<scope>test</scope>
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</dependency>
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<dependency>
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<groupId>org.projectlombok</groupId>
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<artifactId>lombok</artifactId>
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<version>${lombok.version}</version>
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<scope>provided</scope>
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</dependency>
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<!-- 日志框架 -->
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<dependency>
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<groupId>org.slf4j</groupId>
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<artifactId>slf4j-api</artifactId>
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<version>${slf4j.version}</version>
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</dependency>
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<dependency>
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<groupId>ch.qos.logback</groupId>
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<artifactId>logback-classic</artifactId>
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<version>${logback.version}</version>
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<scope>runtime</scope>
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</dependency>
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</dependencies>
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</project>

‎src/main/java/cn/navyd/lib/App.java‎

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package cn.navyd.lib;
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/**
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* Hello world!
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*
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*/
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public class App
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{
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public static void main( String[] args )
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{
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System.out.println( "Hello World!" );
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}
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}

‎src/main/java/cn/navyd/lib/algs/graph/AcyclicLP.java‎

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package cn.navyd.lib.algs.graph;
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import cn.navyd.lib.algs.util.In;
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import cn.navyd.lib.algs.util.ArrayStack;
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/**
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* 无环加权有向图的单点最长路径算法：<br>
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* 与最短路径算法相似，这里只是修改了distTo的初始值为负无穷
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* 并改变relax中不等式的方向
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* @author Navy D
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* @date 20170912180300
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*/
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public class AcyclicLP {
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// 最长路径的边
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private DirectedEdge[] edgeTo;
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// 最长路径
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private double[] distTo;
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public AcyclicLP(EdgeWeightedDigraph g, int s) {
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edgeTo = new DirectedEdge[g.getV()];
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distTo = new double[g.getV()];
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validateVertex(s);
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// 将每个顶点初始化为负无穷
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for (int v = 0; v < g.getV(); v++)
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distTo[v] = Double.NEGATIVE_INFINITY;
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distTo[s] = 0.0;
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// 使用拓扑排序的顶点顺序作为取到顶点权重最小的边
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Topological top = new TopologicalDFS(g);
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if (!top.hasOrder())
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throw new IllegalArgumentException("Digraph is not acyclic.");
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for (int v : top.order())
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// 放松每个顶点
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relax(g, v);
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}
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private void relax(EdgeWeightedDigraph g, int v) {
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for (DirectedEdge e : g.adj(v)) {
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int w = e.to();
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// 取更大的路径长度
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if (distTo[w] < distTo[v] + e.weight()) {
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distTo[w] = distTo[v] + e.weight();
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edgeTo[w] = e;
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}
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}
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}
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/**
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* 返回从起点s到顶点v的最长距离
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* @param v
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* @return
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* @author Navy D
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* @date 20170917113226
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*/
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public double distTo(int v) {
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validateVertex(v);
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return distTo[v];
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}
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/**
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* 如果图中存在从s到达顶点v的最长路径就返回true
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* @param v
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* @return
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* @author Navy D
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* @date 20170917113307
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*/
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public boolean hasPathTo(int v) {
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validateVertex(v);
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return distTo[v] > Double.NEGATIVE_INFINITY;
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}
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/**
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* 返回起点s到顶点v的最长路径集合，如果不存在这个路径就返回null
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* @param v
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* @return
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* @author Navy D
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* @date 20170917113852
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*/
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public Iterable<DirectedEdge> pathTo(int v) {
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validateVertex(v);
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if (!hasPathTo(v))
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return null;
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ArrayStack<DirectedEdge> path = new ArrayStack<>();
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for (DirectedEdge e = edgeTo[v]; e != null; e = edgeTo[e.from()]) {
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path.push(e);
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}
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return path;
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}
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private void validateVertex(int v) {
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if (v < 0 || v >= distTo.length)
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throw new IllegalArgumentException("vertex " + v + " is not between 0 and " + (distTo.length-1));
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}
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public static void main(String[] args) {
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EdgeWeightedDigraph G = new EdgeWeightedDigraph(new In("../Algs_4/tinyEWDAG.txt"));
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int s = 1;
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AcyclicLP lp = new AcyclicLP(G, s);
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for (int v = 0; v < G.getV(); v++) {
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if (lp.hasPathTo(v)) {
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System.out.printf("%d to %d (%.2f) ", s, v, lp.distTo(v));
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for (DirectedEdge e : lp.pathTo(v)) {
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System.out.print(e + " ");
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}
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System.out.println();
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}
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else {
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System.out.printf("%d to %d no path\n", s, v);
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}
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}
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}
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}

‎src/main/java/cn/navyd/lib/algs/graph/AcyclicSP.java‎

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package cn.navyd.lib.algs.graph;
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import cn.navyd.lib.algs.util.In;
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import cn.navyd.lib.algs.util.ArrayStack;
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/**
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* 无环加权有向图的最短路径算法：<br>
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* 思想：按照拓扑排序的顺序放松每个顶点。因为拓扑顺序的顶点w除了之前的顶点v是不会有顶点指向w的，
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* 顶点w除了树中的路径v指向，没有树外的顶点指向边了，一旦顶点w加入最短路径中，路径不会再变化。<br>
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* 复杂度：所需时间为e+v
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* @author Navy D
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* @date 20170912172917
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*/
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public class AcyclicSP implements ShortestPath {
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// 最短路径的存储数组
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private DirectedEdge[] edgeTo;
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// 最短路径权重edgeTo[v] = s->v 最短路径权值
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private double[] distTo;
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/**
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* 在一个无环有向图计算从起点s开始的最短路径
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* @param g
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* @param s
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*/
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public AcyclicSP(EdgeWeightedDigraph g, int s) {
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edgeTo = new DirectedEdge[g.getV()];
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distTo = new double[g.getV()];
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validateVertex(s);
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// 将所有顶点距离初始化最大
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for (int v = 0; v < g.getV(); v++)
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distTo[v] = Double.POSITIVE_INFINITY;
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// 初始化起点s
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distTo[s] = 0.0;
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// 使用拓扑排序的顶点顺序作为取到顶点权重最小的边
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Topological top = new TopologicalDFS(g);
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// 如果图g含有环
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if (!top.hasOrder())
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throw new IllegalArgumentException("Digraph is not acyclic.");
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for (int v : top.order())
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// 放松每个顶点
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relax(g, v);
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}
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/**
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* 顶点的松弛：
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* 对于给定顶点的所有边，检查每条边v-w的最短路径是否是当前路径s-v-w最短，如果是则更新路径
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* @param g
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* @param v
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* @author Navy D
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* @date 20170912172541
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*/
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private void relax(EdgeWeightedDigraph g, int v) {
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for (DirectedEdge e : g.adj(v)) {
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int w = e.to();
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// 如果发现加上当前顶点边v-w比之前树中边连接距离要短就更新
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if (distTo[w] > distTo[v] + e.weight()) {
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distTo[w] = distTo[v] + e.weight();
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edgeTo[w] = e;
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}
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}
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}
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/**
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* 返回从起点s到顶点v的最短距离
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* @param v
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* @return
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* @author Navy D
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* @date 20170917113226
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*/
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public double distTo(int v) {
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validateVertex(v);
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return distTo[v];
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}
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/**
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* 如果图中存在从s到达顶点v的最短路径就返回true
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* @param v
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* @return
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* @author Navy D
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* @date 20170917113307
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*/
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public boolean hasPathTo(int v) {
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validateVertex(v);
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return distTo[v] < Double.POSITIVE_INFINITY;
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}
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/**
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* 返回起点s到顶点v的最短路径集合，如果不存在这个路径就返回null
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* @param v
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* @return
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* @author Navy D
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* @date 20170917113852
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*/
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public Iterable<DirectedEdge> pathTo(int v) {
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validateVertex(v);
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if (!hasPathTo(v))
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return null;
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ArrayStack<DirectedEdge> path = new ArrayStack<>();
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for (DirectedEdge e = edgeTo[v]; e != null; e = edgeTo[e.from()]) {
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path.push(e);
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}
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return path;
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}
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private void validateVertex(int v) {
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if (v < 0 || v >= distTo.length)
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throw new IllegalArgumentException("vertex " + v + " is not between 0 and " + (distTo.length-1));
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}
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public static void main(String[] args) {
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EdgeWeightedDigraph g = new EdgeWeightedDigraph(new In("./tinyEWDAG.txt"));
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int s = 1;
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AcyclicSP sp = new AcyclicSP(g, s);
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for (int v = 0; v < g.getV(); v++) {
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if (sp.hasPathTo(v)) {
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System.out.printf("%d to %d (%.2f) ", s, v, sp.distTo(v));
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for (DirectedEdge e : sp.pathTo(v)) {
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System.out.print(e + " ");
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}
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System.out.println();
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}
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else {
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System.out.printf("%d to %d no path\n", s, v);
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}
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}
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}
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}

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