Compilare: user.cpp: In function ‘void merge(str&, str&, int, int)’: user.cpp:208:41: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int i = 0; i < mst1.first.size(); i ++ ) ^ user.cpp:216:42: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int i = 1; i < mst1.second.size(); i ++ ) { ^ user.cpp:231:42: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int i = 1; i < mst2.second.size(); i ++ ) { ^ user.cpp:241:49: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int i = 0, j = 0; i < mst1.second.size() && j < mst2.second.size(); ) { ^ user.cpp:241:75: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int i = 0, j = 0; i < mst1.second.size() && j < mst2.second.size(); ) { ^ user.cpp:259:41: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int i = 0; i < mst1.first.size(); i ++ ) { ^ user.cpp: In member function ‘char InParser::read_ch()’: user.cpp:14:38: 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); ^