Compilare: user.cpp: In function ‘int main()’: user.cpp:47:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<ctc.size(); ++i) { ^ user.cpp:48:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=0; j<ctc[i].size(); ++j) cout<<ctc[i][j]<<' '; ^ user.cpp:38:32: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("ctc.in","r",stdin); ^ user.cpp:39:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("ctc.out","w",stdout); ^