Compilare: user.cpp: In function ‘int main()’: user.cpp:29:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(j < v[i-1].size() && j < v[i].size() && v[i-1][j] == v[i][j]) ++ j; ^ user.cpp:29:50: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(j < v[i-1].size() && j < v[i].size() && v[i-1][j] == v[i][j]) ++ j; ^ user.cpp:16:32: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("dictree.in","r",stdin); ^ user.cpp:17:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("dictree.out","w",stdout); ^