Compilare: main.cpp: In function 'int main()': main.cpp:28:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < str.length(); ++i) { ~~^~~~~~~~~~~~~~ main.cpp:21:37: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("basequery.in", "r", stdin); ^ main.cpp:22:39: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("basequery.out", "w", stdout); ^