Compilare: main.cpp: In function 'int main()': main.cpp:21:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=0;j<h[i].size();j++) ~^~~~~~~~~~~~ main.cpp:10:34: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("fft2d.in","r",stdin); ^ main.cpp:11:36: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("fft2d.out","w",stdout); ^ main.cpp:13:24: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&f,&n); ^ main.cpp:16:28: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&y,&x); ^