import java.util.ArrayList;
import java.util.Collections;
import java.util.HashSet;
import java.util.LinkedHashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Queue;
import java.util.Set;// 顶点类
class Vertex{String name;// 名称boolean visited;// 是否已访问过public Vertex(String name){this.name=name;this.visited=false;}
}// 图类
public class Graph{// 图private Vertex[] arr;// 顶点数组private int[][] matrix;// 邻接矩阵// 建立图的数据private Set<String> vertexSet;// 包含不重复顶点的集合private Map<String,String[]> connMap;// 包含连接的哈希表// 添加顶点之间的连接关系public void addConn(String from,String[] toArr){if(vertexSet==null){vertexSet=new HashSet<String>();}vertexSet.add(from);for(String to:toArr){vertexSet.add(to);}if(connMap==null){connMap=new LinkedHashMap<String,String[]>();}connMap.put(from, toArr);}// 建立图（即其中的顶点数组和邻接矩阵）public void rebuildGraph(){// 初始化顶点数组List<String> ls=new ArrayList<String>();ls.addAll(vertexSet);Collections.sort(ls);int size=ls.size();arr=new Vertex[size];for(int i=0;i<ls.size();i++){arr[i]=new Vertex(ls.get(i));}// 初始化邻接矩阵matrix=new int[size][size];for(String key:connMap.keySet()){String[] values=connMap.get(key);for(String value:values){int x=findVertexIndex(key);int y=findVertexIndex(value);if(x!=-1 && y!=-1){matrix[x][y]=1;matrix[y][x]=1;}}}}// 在顶点数组里找顶点下标private int findVertexIndex(String name){for(int i=0;i<arr.length;i++){if(name.equals(arr[i].name)){return i;}}return -1;}public void displayMatix(){int n=arr.length;System.out.print("  ");for(int i=0;i<n;i++){System.out.print(arr[i].name+",");}System.out.println();System.out.print("-");for(int i=0;i<n;i++){System.out.print("--");}System.out.println();for(int i=0;i<n;i++){System.out.print(arr[i].name+":");for(int j=0;j<n;j++){System.out.print(matrix[i][j]+",");}System.out.println();}}// 得到两个点之间的路径（深度优先搜索）public String getPath(String from,String to){resetArr();// 初始化int fromIndex=findVertexIndex(from);if(fromIndex==-1){return "找不到顶点:"+from;}int toIndex=findVertexIndex(to);if(toIndex==-1){return "找不到顶点:"+to;}//  用于记住路径的栈Stack<Integer> stack=new Stack<Integer>(Integer.class,arr.length);// 开始寻找arr[fromIndex].visited=true;stack.push(fromIndex);while(stack.isEmpty()==false){int j=getConnVertex(stack.peek());if(j==-1){stack.pop();}else{arr[j].visited=true;stack.push(j);if(arr[j].name.equals(to)){// 找到了
                    StringBuilder sb=new StringBuilder();while(stack.isEmpty()==false){int index=stack.pop();sb.insert(0, arr[index].name+"->");}return sb.substring(0, sb.length()-2);}}}return "不可能从"+from+"到"+to;}// 广度优先搜索public String getPath2(String from,String to){resetArr();// 初始化int fromIndex=findVertexIndex(from);if(fromIndex==-1){return "找不到顶点:"+from;}int toIndex=findVertexIndex(to);if(toIndex==-1){return "找不到顶点:"+to;}// 用于记住路径的队列Queue<Integer> queue=new LinkedList<Integer>();// 开始寻找StringBuilder sb=new StringBuilder();arr[fromIndex].visited=true;queue.add(fromIndex);sb.append(arr[fromIndex].name+"->");int j;while(queue.isEmpty()==false){int i=queue.remove();while((j=getConnVertex(i))!=-1){arr[j].visited=true;sb.append(arr[j].name+"->");queue.add(j);if(arr[j].name.equals(to)){// 找到了return sb.substring(0, sb.length()-2);}}}return "不可能从"+from+"到"+to;}/*** 重置顶点访问情况*/private void resetArr(){int n=arr.length;for(int j=0;j<n;j++){arr[j].visited=false;}}// 取得连接未访问过的顶点private int getConnVertex(int i){int n=arr.length;for(int j=0;j<n;j++){if(matrix[i][j]==1 && arr[j].visited==false){return j;}}return -1;}public static void main(String[] args){Graph g=new Graph();g.addConn("A", new String[]{"B","D"});g.addConn("B", new String[]{"A","C"});g.addConn("C", new String[]{"B","D","E"});g.addConn("D", new String[]{"A","C"});g.addConn("E", new String[]{"C"});g.addConn("F", new String[]{"E","G"});g.addConn("G", new String[]{"F"});g.addConn("H", new String[]{"I","J"});g.addConn("I", new String[]{"H","J"});g.addConn("J", new String[]{"H","I"});g.rebuildGraph();g.displayMatix();String path=g.getPath("A", "G");System.out.println(path);path=g.getPath("A", "H");System.out.println(path);path=g.getPath("J", "H");System.out.println(path);path=g.getPath("F", "B");System.out.println(path);path=g.getPath2("A", "G");System.out.println(path);path=g.getPath2("F", "B");System.out.println(path);}
}

  A,B,C,D,E,F,G,H,I,J,
---------------------
A:0,1,0,1,0,0,0,0,0,0,
B:1,0,1,0,0,0,0,0,0,0,
C:0,1,0,1,1,0,0,0,0,0,
D:1,0,1,0,0,0,0,0,0,0,
E:0,0,1,0,0,1,0,0,0,0,
F:0,0,0,0,1,0,1,0,0,0,
G:0,0,0,0,0,1,0,0,0,0,
H:0,0,0,0,0,0,0,0,1,1,
I:0,0,0,0,0,0,0,1,0,1,
J:0,0,0,0,0,0,0,1,1,0,
A->B->C->E->F->G
不可能从A到H
J->H
F->E->C->B
A->B->D->C->E->F->G
F->E->G->C->B