Compilare: user.cpp: In function ‘std::ostream& operator<<(std::ostream&, const Container&)’: user.cpp:35:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < obj.N; ++i) ^ user.cpp: In member function ‘void Container::_qsort(int, int)’: user.cpp:71:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(vec[ i ] < piv) i++; ^ user.cpp:73:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(vec[ j ] > piv) j--; ^ user.cpp: In function ‘int main()’: user.cpp:106:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < N; i++) { ^ user.cpp:92:29: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen(FIN, "r", stdin); ^ user.cpp:94:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d\n",&N); ^ user.cpp:98:16: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets( str ); ^ /tmp/cckR90Sv.o: In function `main': user.cpp:(.text.startup+0x7f): warning: the `gets' function is dangerous and should not be used.