Compilare: main.cpp: In function 'bool check(int)': main.cpp:13:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < strlen(t); i++) { ~~^~~~~~~~~~~ main.cpp:15:27: 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:23:40: 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:24:42: 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); ^ main.cpp:27:33: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d %s", &n, &q, s); ^ main.cpp:30:23: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%s", t); ^