Repeated Substring Pattern

Given a non-empty string check if it can be constructed by taking a substring of it and appending multiple copies of the substring together. You may assume the given string consists of lowercase English letters only and its length will not exceed 10000.

Example 1:

Input: "abab"

Output: True

Explanation: It's the substring "ab" twice.

Example 2:

Input: "aba"

Output: False

Example 3:

Input: "abcabcabcabc"

Output: True

Explanation: It's the substring "abc" four times. (And the substring "abcabc" twice.)

分析

2个s相连，去首尾char，得到T，然后看看s在不在T里。

找到s在T里出现的第一个位置i，重复的字符的长度是i+1，重复字符是s(0,i+1)

class Solution {
    public boolean repeatedSubstringPattern(String s) {
        if(s == null || s.length() == 0)
            return true;
        String ss = s + s;
        String t = ss.substring(1, ss.length() - 1);
        return t.indexOf(s) >= 0;
    }
}