字符串组合（包括去重判断）

列如 abc输出 a,b,c ab ac bc abc

aabc  输出 a,b,c ab,ac,aab,aac,abc,aabc

public class T {public static Stack<String>s=new Stack<String>();public static String a="aabbcdef";public static int count=0;/** * @param args */public static void main(String[] args) {// TODO Auto-generated method stub     combine(0);     System.out.println(count);}private static void combine(int index) {// TODO Auto-generated method stubif(index>a.length()-1) return;    s.push(a.charAt(index)+" ");combine(index+1);print(s);    s.pop();    while(index<a.length()-1 && a.charAt(index)==a.charAt(index+1))    {    index++;    }    combine(index+1);}private static void print(Stack<String> s2) {// TODO Auto-generated method stubfor(String i:s2){System.out.print(i.trim());}count++;System.out.println();}}