Compilare: user.cpp: In function ‘void FFT(std::vector<cp>&, bool)’: user.cpp:35:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0;i<A.size();i++) if (i<rev(i,lg)) swap(A[i],A[rev(i,lg)]); ~^~~~~~~~~ user.cpp:37:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int len = 2; len <= A.size(); len<<=1){ ~~~~^~~~~~~~~~~ user.cpp:40:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0;i<A.size();i+=len){ ~^~~~~~~~~ user.cpp:50:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0;i<A.size() && inv;i++) A[i] /= A.size(); ~^~~~~~~~~ user.cpp: In function ‘std::vector<int> mul(std::vector<cp>, std::vector<cp>)’: user.cpp:64:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0;i<A.size() + B.size() - 1;i++) ans.push_back(_C[i].real() + 0.5); ~^~~~~~~~~~~~~~~~~~~~~~~~ user.cpp: In function ‘int main()’: user.cpp:90:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0;i<ans.size();i++) if (ans[i]) fprintf(g,"%d %d\n",i,ans[i]); ~^~~~~~~~~~~ user.cpp:71:22: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f,"%d",&t); ^ user.cpp:76:26: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f,"%d",&n); ^ user.cpp:79:30: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f,"%d",&x); ^ user.cpp:82:26: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f,"%d",&m); ^ user.cpp:84:30: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f,"%d",&x); ^