KMP prefix function

KMP_prefix.cpp

std::vector<unsigned> kmp_prefix_function(std::string s) {
    size_t n = s.size();
    std::vector<unsigned> result(n);
    
    for (int i = 1; i < n; i++) {
        int j = result[i-1];
        
        while (j > 0 && s[i] != s[j])
            j = result[j-1];
        
        if (s[i] == s[j]) j++;
        result[i] = j;
    }
    return result;
}

int main(int argc, char ** argv) {
    std::vector<unsigned> a = kmp_prefix_function("abcabcd");
    for (int i = 0; i < a.size(); i++)
        std::cout << a[i] << " ";
    std::cout << std::endl;
    
    return 0;
}