leetcode 459. 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.)

    public boolean repeatedSubstringPattern(String s) {
        int length = s.length();
        //i为子字符串长度
        for(int i = length / 2 ; i>=1 ; i--) {
            if(length % i == 0) {
                //重复的次数
                int repeatCount = length / i;
                //假设的重复的子字符串
                String subString = s.substring(0, i);
                int j = 1;
                for( ; j<repeatCount ; j++) {
                    //一旦有一个子字符串不等，就可以退出比较
                    if(!subString.equals(s.substring(j * i, (j + 1) * i))){
                        break;
                    }
                }
                //达到重复次数
                if(j == repeatCount) {
                    return true;
                }
            }
        }
        return false;
    }