Repeated Substring Pattern

Description:

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.

Ex:

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.)

问题描述：

给一个字符串，判断是否能够由重复的子字符串组成。

解法一：

思路：

1.重复子串的长度必须是原始字符串的除数( 整除)
2. 为了找到这个除数，从length/2 开始
3. 然后把m 次子字符串拼接起来，是否与原始字符串相等

另外这里做了优化，在m次比较过程中，发现不等，直接break..

Code:

public class Solution {    public boolean repeatedSubstringPattern(String s) {        int len = s.length();        for (int i = len / 2;i >= 1;i--){            if (len % i == 0){                int m = len / i;                String subS = s.substring(0, i);                int j;                for (j = 1; j < m; j++){                    if (!subS.equals(s.substring(j * i, i + j * i))){                        break;                    }                }                if (j == m){                    return true;                }              }            }              return false;        }    }