1 package org.xiu68.exp.exp9;
2
3 import java.util.Stack;
4
5 public class Exp9_3 {
6 //无向图的双连通分量问题
7 public static void main(String[] args) {
8 // TODO Auto-generated method stub
9 int[][] graph=new int[][]{
10 {0,1,1,0,0},
11 {1,0,1,0,0},
12 {1,1,0,1,1},
13 {0,0,1,0,1},
14 {0,0,1,1,0}
15 };
16 MGraph1 m=new MGraph1(graph);
17 m.bicompDFS(0);
18 }
19
20 }
21
22
23 //邻接矩阵表示无向图
24 class MGraph1{
25 private int vexNum; //顶点数量
26 private int[][] edges; //边
27 private Stack<Edge> edgeStack; //边栈
28 private int[] color; //记录顶点的访问状态，-1为未访问到,0为正在搜索中,1为已搜索完成
29 private int[] pre; //记录顶点的访问时间
30 private int[] post; //记录顶点的结束访问时刻
31 private int clock; //访问时刻
32
33 public MGraph1(int[][] edges) {
34 this.edges = edges;
35 this.vexNum=edges.length;
36 this.color=new int[vexNum];
37 this.pre=new int[vexNum];
38 this.post=new int[vexNum];
39 this.clock=1;
40 this.edgeStack=new Stack<>();
41
42 //初始化所有结点为未访问状态
43 for(int i=0;i<vexNum;i++){
44 color[i]=-1;
45 }
46 }
47
48
49 public int bicompDFS(int v){
50 //color[v]的值：-1为未访问到,0为正在搜索中,1为已搜索完成
51 color[v]=0; //顶点v正在搜索中
52 pre[v]=clock; //顶点v的访问时刻
53 clock++;
54
55 int back=pre[v]; //表示从v出发，经过一条其后代组成的边包括回退边,所能访问到的顶点的最小的开始搜索时间
56
57 for(int i=0;i<vexNum;i++){
58 if(edges[v][i]==1 && color[i]!=1){
59
60 edgeStack.push(new Edge(v,i)); //放入边栈中
61
62 if(color[i]==-1){ //树边
63 int wBack=bicompDFS(i);
64
65 if(wBack>=pre[v]){ //说明v的子树没有回路关联到v的祖先
66 System.out.println("双连通部件: ");
67 Edge e=edgeStack.pop();
68 while(true){
69 System.out.println("("+e.getHead()+","+e.getTail()+") ");
70 if(e.getHead()==v && e.getTail()==i)
71 break;
72 e=edgeStack.pop();
73 }
74 }
75 if(wBack<back)
76 back=wBack;
77 }else if(color[i]==0){ //回边
78 if(pre[i]<back)
79 back=pre[i];
80 }
81 }//if
82 }//for
83
84 post[v]=clock;
85 clock++;
86 color[v]=1;
87 return back;
88 }
89 }
90
91 class Edge{
92 private int head; //边的头
93 private int tail; //边的尾
94
95 public Edge(int head,int tail){
96 this.head=head;
97 this.tail=tail;
98 }
99
100 public int getHead() {
101 return head;
102 }
103
104 public void setHead(int head) {
105 this.head = head;
106 }
107
108 public int getTail() {
109 return tail;
110 }
111
112 public void setTail(int tail) {
113 this.tail = tail;
114 }
115
116 }
