Compilare: main.cpp: In function 'int _(std::vector<std::complex<double> >&, int)': main.cpp:2:293: warning: no return statement in function returning non-void [-Wreturn-type] 2 | using namespace std;const int N=1<<16;int _(vector<complex<double>>&a,int q){int n=a.size(),i,r,j;auto b=a;for(r=n/2;r;r/=2){for(i=0;i<n/2;i+=r){auto w=pow(M_E,(q?-i:i)*M_PI/n*2.0i);for(j=0;j<r;++j){auto u=a[i*2+j],v=w*a[i*2+j+r];b[i+j]=u+v;b[i+n/2+j]=u-v;}}swap(a,b);}if(q)for(auto&x:a)x/=n;}main(){ifstream g("bacterii2.in");ofstream l("bacterii2.out");int t,n,x,i,o,m;g>>t;while(t--){vector<complex<double>>p(N),q(N);g>>n;while(n--){;g>>x;p[x]+=1;}g>>m;while(m--){;g>>x;q[x]+=1;}_(p,0);_(q,0);for(i=0;i<N;++i)p[i]*=q[i];_(p,1);for(i=0;i<N;++i){o=real(p[i])+0.5;if(o>0)l<<i<<" "<<o<<'\n';}l<<'\n';}} | ^ main.cpp: At global scope: main.cpp:2:294: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type] 2 | using namespace std;const int N=1<<16;int _(vector<complex<double>>&a,int q){int n=a.size(),i,r,j;auto b=a;for(r=n/2;r;r/=2){for(i=0;i<n/2;i+=r){auto w=pow(M_E,(q?-i:i)*M_PI/n*2.0i);for(j=0;j<r;++j){auto u=a[i*2+j],v=w*a[i*2+j+r];b[i+j]=u+v;b[i+n/2+j]=u-v;}}swap(a,b);}if(q)for(auto&x:a)x/=n;}main(){ifstream g("bacterii2.in");ofstream l("bacterii2.out");int t,n,x,i,o,m;g>>t;while(t--){vector<complex<double>>p(N),q(N);g>>n;while(n--){;g>>x;p[x]+=1;}g>>m;while(m--){;g>>x;q[x]+=1;}_(p,0);_(q,0);for(i=0;i<N;++i)p[i]*=q[i];_(p,1);for(i=0;i<N;++i){o=real(p[i])+0.5;if(o>0)l<<i<<" "<<o<<'\n';}l<<'\n';}} | ^~~~