题目：

题解：

class Solution {public boolean repeatedSubstringPattern(String s) {return kmp(s + s, s);}public boolean kmp(String query, String pattern) {int n = query.length();int m = pattern.length();int[] fail = new int[m];Arrays.fill(fail, -1);for (int i = 1; i < m; ++i) {int j = fail[i - 1];while (j != -1 && pattern.charAt(j + 1) != pattern.charAt(i)) {j = fail[j];}if (pattern.charAt(j + 1) == pattern.charAt(i)) {fail[i] = j + 1;}}int match = -1;for (int i = 1; i < n - 1; ++i) {while (match != -1 && pattern.charAt(match + 1) != query.charAt(i)) {match = fail[match];}if (pattern.charAt(match + 1) == query.charAt(i)) {++match;if (match == m - 1) {return true;}}}return false;}
}