Compilare: main.cpp: In function 'void unite(int, int)': main.cpp:28:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (stuff[y].size() == i) best = max(best, sz[y]); ~~~~~~~~~~~~~~~~^~~~ main.cpp: In function 'int main()': main.cpp:34:37: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("unique.in", "r", stdin); ^ main.cpp:35:39: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("unique.out", "w", stdout); ^