459. Repeated Substring Pattern | 字符串重复子串序列

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.)

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思路，这道题应该用kmp算法的，奈何无法写出kmp算法，就用了一个时间更长的算法，即通过遍历子串，如果子串重复链接可以得到字符串的话就返回TRUE。

public class Solution {
   		public boolean repeatedSubstringPattern(String s) {
		int len = s.length();
		String sub = "";
		StringBuilder stringBuilder = new StringBuilder();
		for(int i= len/2;i>=1;i--){
			if (len%i==0) {
				int m = len/i;
				sub = s.substring(0, i);
				for(int k = 0;k