Compilare: main.cpp: In function 'bool check(int)': main.cpp:11:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < t.length(); i++) { ~~^~~~~~~~~~~~ main.cpp:13:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (pos + mid - 1 >= vec[t[i] - 'a'].size()) return false; ~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:21:40: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("balbaiala.in", "r", stdin); ^ main.cpp:22:42: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("balbaiala.out", "w", stdout); ^