字符串排列

import java.util.ArrayList;
import java.util.Arrays;
public class Solution {
    public ArrayList<String> Permutation(String str) {
        int len=str.length();
        ArrayList<String> list=new ArrayList<>();
        if(len==0){
            return list;
        }
        //对字符串进行排序
        String[] ref=new String[len];
        for(int i=0;i<str.length();i++){
            ref[i]=str.charAt(i)+"";
        }
        Arrays.sort(ref);
        StringBuilder sb=new StringBuilder("");
        boolean[] bo=new boolean[str.length()];
        for(int i=0;i<ref.length;i++){
            sb.append(ref[i]);
        }
        str=sb.toString();
        StringBuilder sb1=new StringBuilder("");
        find(sb1,bo,list,str);
        return list;
    }
    public void find(StringBuilder sb,boolean[] bo,ArrayList<String> list,String c){
        if(sb.length()==c.length()){
            list.add(new String(sb.toString()));
            return;
        }
        for(int i=0;i<c.length();i++){
            if(bo[i]==false){
                bo[i]=true;
                String f=c.charAt(i)+"";
                find(new StringBuilder(sb.append(f)),bo,list,c);
                sb.delete(sb.length()-1,sb.length());
                bo[i]=false;
                //当前为的字符不能一样，
                if(i<c.length()-1&&(c.charAt(i)+"").equals(c.charAt(i+1)+"")){
                        i++;
                }
                 
            }
        }
    }
}