Compilare: user.cpp: In function ‘void backtracking(int)’: user.cpp:77:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(j < pList[i].size() && pTaken.find(pList[i][j]) == pTaken.end()) { ^ user.cpp:80:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(j == pList[i].size()) { ^ user.cpp:81:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j = 0; j < pList[i].size(); j++) { ^ user.cpp: In member function ‘void InputReader::advance()’: user.cpp:35:51: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fread(buffer, SIZE, 1, input_file); ^ user.cpp: In constructor ‘InputReader::InputReader(const char*)’: user.cpp:13:47: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fread(buffer, SIZE, 1, input_file); ^