有6个英文字母,a,b,c ,d,e,f
 从中任意取N个(N<=6)来排列.
已知 a 只能与 b 相连, 
         b不能和e,f相连
         c不能和a相连
         d不能和 a ,e相连
           f 不能和 a,b相连
请打印出字母f或b 在末尾的组合顺序,用Java实现

我的解答:

    import java.util.*;

/**
 *
 * @author ShenXiaoliang
 *
 */
public class DemoGraph {
 
 final static int VERTICE=6;
 
 private ArrayList<String> patheSet=new ArrayList<String>();
 
 private String[] ver={"a","b","c","d","e","f"};
 
 private int[][] graph=new int[6][6];
 
 private String path="";
 
 private boolean[] isVisit=new boolean[VERTICE];
 
 
 public DemoGraph() {
  
  initiGraph();
  for(int index=0;index<VERTICE;index++)
  depthSearch(index);
  show();
  
 }
 
 private void initiGraph(){
  graph[0][1]=1;
  graph[1][0]=1;
  graph[1][2]=1;
  graph[1][3]=1;
  graph[2][1]=1;
  graph[2][3]=1;
  graph[2][4]=1;
  graph[2][5]=1;
  graph[3][1]=1;
  graph[3][2]=1;
  graph[3][5]=1;
  graph[4][2]=1;
  graph[4][5]=1;
  graph[5][2]=1;
  graph[5][3]=1;
  graph[5][4]=1;
 }
 
 private void depthSearch(int start){
  
  isVisit[start]=true;
  path+=ver[start];
  if(path.charAt(path.length()-1)=='f'||path.charAt(path.length()-1)=='b') patheSet.add(path);
  for(int index=0;index<VERTICE;index++)
   if(graph[start][index]==1&&isVisit[index]==false)
    depthSearch(index);
   else continue;
  path=path.substring(0,path.length()-1);
  isVisit[start]=false;
 }
 
 
 private void show(){
  for(String pa:patheSet)
   System.out.println(pa);
 }

 /**
  * @param args
  */
 public static void main(String[] args) {
  // TODO Auto-generated method stub
  new DemoGraph();
 }

}