Compilare: user.cpp: In function ‘int main()’: user.cpp:80:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < A.size(); i++) { ^ user.cpp:65:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("huffman.in","r",stdin); ^ user.cpp:66:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("huffman.out","w",stdout); ^ user.cpp:67:17: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &N); ^ user.cpp:72:27: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &A[i]->Freq); ^