Java递归实现全排列改进(一)---利用HashSet实现去重

import java.util.ArrayList;

import java.util.Arrays;

import java.util.HashSet;

import java.util.Iterator;

import java.util.List;

import java.util.Set;

public class Test{

 private static String[] s = new String[]{"a","b","a"};

 private static int l = s.length;

 private static Set<String> set = new HashSet<String>();

 public static void main(String[] args) {

  List<String> source = Arrays.asList(s);

  List<String> target = new ArrayList<String>();

  sort(source,target);

  Iterator<String> it = set.iterator();

  while(it.hasNext()){

   System.out.println(it.next());

  }

 }

 private static void sort(List<String> source, List<String> target) {

  if(target.size() == l){

   set.add(target.toString().replaceAll(",", "").replace("[", "").replace("]", "").replace(" ", ""));

  }

  for(int i=0;i<source.size();i++){

   List<String> targetList = new ArrayList<String>(target);

   targetList.add(source.get(i));

   List<String> resourceList = new ArrayList<String>(source);

   resourceList.remove(i);

   sort(resourceList,targetList);

  }

 }

}