Compilare: user.cpp: In function ‘void gen(int)’: user.cpp:13:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(v.size()<res) { ^ user.cpp:16:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<v.size();i++) ans.push_back(v[i]); ^ user.cpp:22:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<v.size();i++) { ^ user.cpp:24:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=0;j<v[i].size();j++) { ^ user.cpp: In function ‘int main()’: user.cpp:65:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=0;j<ans[i].size();j++) cout<<' '<<ans[i][j]; ^ user.cpp:47:31: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("dubi.in","r",stdin); ^ user.cpp:48:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("dubi.out","w",stdout); ^