前言

有向图（Directed Graph）是一种由顶点和有方向的边组成的图数据结构。

实现原理

使用邻接表表示法实现有向图相对简单明了，步骤也相对简单。

1:首先创建有向图

2.创建顶点

3.顶点间创建边

具体代码实现

package test13;import java.util.*;
class Vertex {private String label;public Vertex(String label) {this.label = label;}public String getLabel() {return label;}@Overridepublic boolean equals(Object obj) {if (this == obj) return true;if (obj == null || getClass() != obj.getClass()) return false;Vertex vertex = (Vertex) obj;return label.equals(vertex.label);}@Overridepublic int hashCode() {return label.hashCode();}@Overridepublic String toString() {return label;}
}class DirectedGraph {private Map<Vertex, List<Vertex>> adjVertices;public DirectedGraph() {adjVertices = new HashMap<>();}public void addVertex(String label) {adjVertices.putIfAbsent(new Vertex(label), new ArrayList<>());}public void removeVertex(String label) {Vertex v = new Vertex(label);adjVertices.values().forEach(e -> e.remove(v));adjVertices.remove(new Vertex(label));}public void addEdge(String label1, String label2) {Vertex v1 = new Vertex(label1);Vertex v2 = new Vertex(label2);adjVertices.get(v1).add(v2);}public void removeEdge(String label1, String label2) {Vertex v1 = new Vertex(label1);Vertex v2 = new Vertex(label2);List<Vertex> eV1 = adjVertices.get(v1);if (eV1 != null)eV1.remove(v2);}public List<Vertex> getAdjVertices(String label) {return adjVertices.get(new Vertex(label));}@Overridepublic String toString() {StringBuilder sb = new StringBuilder();for (Vertex v : adjVertices.keySet()) {sb.append(v).append(": ");for (Vertex w : adjVertices.get(v)) {sb.append(w).append(" ");}sb.append("\n");}return sb.toString();}public static void main(String[] args) {DirectedGraph graph = new DirectedGraph();graph.addVertex("A");graph.addVertex("B");graph.addVertex("C");graph.addVertex("D");graph.addEdge("A", "B");graph.addEdge("A", "C");graph.addEdge("B", "C");graph.addEdge("C", "D");System.out.println(graph);}
}

QA:待定