A string s is LUCKY if and only if the number of different characters in s is a fibonacci number. Gi

题目描述

A string s is LUCKY if and only if the number of different characters in s is a fibonacci number. Given a string consisting of only lower case letters , output all its lucky non-empty substrings in lexicographical order. Same substrings should be printed once. 
输入描述:
a string consisting no more than 100 lower case letters.


输出描述:
output the lucky substrings in lexicographical order.one per line. Same substrings should be printed once.

输入例子:
aabcd

输出例子:
a 
aa 
aab 
aabc 
ab 
abc 
b 
bc 
bcd 
c 
cd 
d

一晚上就做了这一道题，必须纪念下！

才知道TreeSet是有序的，HashSet是无序的，要是把HashSet排序很麻烦。。。

import java.util.ArrayList;
import java.util.Date;
import java.util.HashSet;
import java.util.Iterator;
import java.ut