Compilare: user.cpp: In member function ‘int& my_map::operator[](int)’: user.cpp:28:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < data.size(); i++) ^ user.cpp: In member function ‘void Flow::init(int, int, int)’: user.cpp:58:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < C.size(); i++) { ^ user.cpp: In function ‘int main()’: user.cpp:148:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("smart.in","r",stdin); ^ user.cpp:149:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("smart.out","w",stdout); ^ user.cpp:151:30: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d\n", &n, &how); ^ user.cpp:153:34: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%s\n", mat[i] + 1); ^ user.cpp: In member function ‘int& my_map::operator[](int)’: user.cpp:31:5: warning: control reaches end of non-void function [-Wreturn-type] } ^