题目：

题解：

func repeatedSubstringPattern(s string) bool {
    return kmp(s + s, s)
}

func kmp(query, pattern string) bool {
    n, m := len(query), len(pattern)
    fail := make([]int, m)
    for i := 0; i < m; i++ {
        fail[i] = -1
    }
    for i := 1; i < m; i++ {
        j := fail[i - 1]
        for j != -1 && pattern[j + 1] != pattern[i] {
            j = fail[j]
        }
        if pattern[j + 1] == pattern[i] {
            fail[i] = j + 1
        }
    }
    match := -1
    for i := 1; i < n - 1; i++ {
        for match != -1 && pattern[match + 1] != query[i] {
            match = fail[match]
        }
        if pattern[match + 1] == query[i] {
            match++
            if match == m - 1 {
                return true
            }
        }
    }
    return false
}