JAVA实现图的邻接表以及DFS

JAVA实现图的邻接表以及DFS ⼀：定义邻接表结构储存图
package 图的遍历;
//邻接表实现图的建⽴
//储存边
class EdgeNode {
int index; // 习惯了⽤index，其实标准写法是(adjVertex)
int value; // 权值
EdgeNode nextArc; // 指向下⼀条弧
}
// 邻接表节点的类型
class VertexNode {
String name;
EdgeNode firstArc = new EdgeNode(); // 指向第⼀条弧
}
public class Graph {
VertexNode[] adjList; // 保存邻接表的头节点
int e; // 图的边数
int v; // 图的顶点数
boolean[] visit;
public Graph(int v, int e) {
this.v = v;
this.e = e;
adjList = new VertexNode[e + 1]; // 学习Java养成的好习惯，动态分配空间,创建顶点表数组
visit = new boolean[e + 1]; //标记
for (int i = 0; i < e; i++) {
visit[i] = false;
}
}
}
⼆：DFS过程
package 图的遍历;
public class DFSGraph {
public static void DFS(Graph G, int k) {
System.out.println(G.adjList[k].name);
G.visit[k] = true;
EdgeNode p = new EdgeNode();
p = G.adjList[k].firstArc;
while(p!=null){
if(G.visit[p.index]!=true){
DFS(G,p.index);
}
p=p.nextArc;
}
}
}
三：建⽴图
package 图的遍历;
import java.util.Scanner;
public class CreateGraph {
private static Graph G;
public static Graph getGraph(){
return G;
}
public static void createGraph() {
Scanner sc = new Scanner(System.in);
System.out.println("请输⼊顶点数v和边数e:");
int v = sc.nextInt();
int e = sc.nextInt();
G = new Graph(v, e);
System.out.println("请输⼊各顶点信息:");
for (int i = 0; i < G.v; i++) {
G.adjList[i] = new VertexNode();
G.adjList[i].name = sc.next();
G.adjList[i].firstArc = null; // 不可或缺
}
System.out.println("请输⼊各边信息(⽤空格隔开):");
for (int i = 0; i < G.e; i++) {
EdgeNode en1 = new EdgeNode();
// 保证e1,e2都是合法输⼊
String e1 = sc.next();
String e2 = sc.next();
int v1 = Index(e1);
int v2 = Index(e2);
en1.index = v1; // en1的下标是v1
en1.nextArc = G.adjList[v2].firstArc;
G.adjList[v2].firstArc = en1;
EdgeNode en2 = new EdgeNode();
en2.index = v2; // en2的下标是v2
en2.nextArc = G.adjList[v1].firstArc;
G.adjList[v1].firstArc = en2;
}
}
public static void outputGraph() { //不知道为何空指针异常 try {
System.out.println("输出邻接表存储情况：");
EdgeNode en = new EdgeNode();
for (int i = 0; i < G.e; i++) {
System.out.print(G.adjList[i].name);
en = G.adjList[i].firstArc;
while (en != null) {
System.out.print("->" + G.adjList[en.index].name);
en = en.nextArc;
}
System.out.println();
}
} catch (NullPointerException e) {
}
}
private static int Index(String e1) {
for (int i = 0; i < G.v; i++) {
if (G.adjList[i].name.equals(e1)){
return i;
}
}
return -1;
}
}
四：测试
package 图的遍历;
public class GraphDemo {
public static void main(String[] args) {
CreateGraph.createGraph();
CreateGraph.outputGraph();
System.out.println("DFS图的过程如下：");
DFSGraph.DFS(CreateGraph.getGraph() , 0);
}
}
/*
* 请输⼊顶点数v和边数e: 4 5
* 请输⼊各顶点信息: a b c d
* 请输⼊各边信息(⽤空格隔开):
* a b
* a c
* a d
* b c
* b d
*/
五，测试结果。