Compilare: user.cpp: In function ‘std::pair<int, std::vector<std::tuple<int, int, int> > > online_min_spanning_tree(Graph&, Edge, int)’: user.cpp:107:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < graph.size(); i++) { ^ user.cpp: In function ‘int main()’: user.cpp:129:31: warning: deprecated conversion from string constant to ‘char*’ [-Wwrite-strings] myIfstream cin("online.in"); ^ user.cpp: In constructor ‘myIfstream::myIfstream(char*)’: user.cpp:30:39: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fread (buffer, 1, SIZE, input); ^ user.cpp: In member function ‘void myIfstream::advance()’: user.cpp:23:43: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fread (buffer, 1, SIZE, input); ^ user.cpp: In member function ‘myIfstream& myIfstream::operator>>(int&)’: user.cpp:43:9: warning: ‘last’ may be used uninitialized in this function [-Wmaybe-uninitialized] if (last == '-') ^ user.cpp: In function ‘int main()’: user.cpp:43:9: warning: ‘last’ may be used uninitialized in this function [-Wmaybe-uninitialized] user.cpp:36:14: note: ‘last’ was declared here char last; ^ user.cpp:43:9: warning: ‘last’ may be used uninitialized in this function [-Wmaybe-uninitialized] if (last == '-') ^ user.cpp:36:14: note: ‘last’ was declared here char last; ^