代码：
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); } }
输出：
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
顶点示意图：
本文转自张昺华-sky博客园博客，原文链接：http://www.cnblogs.com/xiandedanteng/p/3885477.html，如需转载请自行联系原作者
