Compilare: main.cpp: In function 'void BFS()': main.cpp:102:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<a[first].size(); ++i) ~^~~~~~~~~~~~~~~~ main.cpp: In member function 'char InParser::read_ch()': main.cpp:17:29: warning: ignoring return value of 'size_t fread(void*, size_t, size_t, FILE*)', declared with attribute warn_unused_result [-Wunused-result] fread(buff, 1, 4096, fin); ^