A*B 原根+FFT优化
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题目地址 https://loj.ac/problem/6156
#include <bits/stdc++.h> const long long mod = 1e9+7; const double ex = 1e-10; #define inf 0x3f3f3f3f using namespace std; const double PI = acos(-1.0); const int MAXN = 60044*4; struct Complex{ double x,y; Complex(double _x = 0.0,double _y =0.0){ x = _x;y =_y; } Complex operator - (const Complex &b)const{ return Complex(x-b.x,y-b.y); } Complex operator + (const Complex &b)const{ return Complex(x+b.x,y+b.y); } Complex operator * (const Complex &b)const{ return Complex(x*b.x - y*b.y,x*b.y + y*b.x); } }; void change (Complex y[],int len){ int i,j,k; for (i = 1,j = len/2;i<len -1;i++){ if (i<j) swap(y[i],y[j]); k = len/2; while (j >= k){ j-=k; k/=2; } if (j<k) j+=k; } } void fft(Complex y[],int len, int on) { change(y,len); for (int h = 2; h<=len;h<<=1){ Complex wn(cos(-on*2*PI/h),sin(-on*2*PI/h)); for (int j =0 ; j< len; j+=h){ Complex w(1,0); for (int k = j;k < j+h/2;k++){ Complex u = y[k]; Complex t = w*y[k+h/2]; y[k] = u+t; y[k+h/2] = u-t; w = w*wn; } } } if (on == -1) for (int i = 0; i<len; i++) y[i].x /= len; } Complex x1[MAXN]; long long x2[MAXN]; long long num[MAXN]; long long ans[MAXN/4]; long long quick_s(long long x,long long y,long long N){ long long ans = 1; while (y){ if (y % 2) ans = (ans * x) % N; x = (x*x) % N; y/=2; } return ans % N; } vector <long long> p; int b[62345]; void getprime(int N){ for (int i = 2;i<=N;i++){ if ( b[i] == 0 ){ p.push_back((long long)i); int j = 2; while (i*j <= N) b[i*j] = 1,j++; } } } int getroot(long long N){ vector <long long> C; C.clear(); long long t = N-1; for (long long i = 0; i<p.size() && p[i]*p[i] <= N; i++){ if (t % p[i] == 0 && t!=1){ C.push_back((N-1)/p[i]); while (t % p[i] == 0 && t!=1) t/=p[i]; } } if (t!=1) C.push_back((N-1)/t); for (long long i = 2 ; i<=N; i++){ int flag = 1; for (int j = 0 ; j< C.size() && flag ; j++ ) if (quick_s(i,C[j],N) == 1&&C[j]!=N-1) flag = 0; if (flag && (quick_s(i,N-1,N) == 1)) return i; } return 0; } int main() { getprime(60000); int T; scanf("%d",&T); while (T--){ long long n,m; scanf("%lld%lld",&n,&m); long long root = getroot(m); memset(num,0,sizeof(num)); memset(x2,0,sizeof(x2)); memset(ans,0,sizeof(ans)); int len1 = m; for (int i = 1; i<=n; i++){ int d; scanf("%d",&d); num[d%m]++; } int len = 1; while (len < len1*2) len <<=1; for (int i = 1; i<m;i++) x1[i] = Complex(num[quick_s(root,i,m)],0); for (int i = m ; i<len ; i++) x1[i] = Complex(0,0); x1[0] = Complex(0,0); fft(x1,len,1); for (int i = 0 ; i<len ; i++) x1[i] = x1[i] * x1[i]; fft(x1,len,-1); ans[0] = num[0] * (num[0]-1)/2 + num[0] * (n-num[0]); printf("%d\n",ans[0]); for (int i = 0; i<=2*m;i++) x2[i] = (long long)(x1[i].x + 0.5); for (long long i = 1; i<m; i++){ long long t = quick_s(root,i,m); x2[2*i] -= num[t] * num[t]; x2[2*i-1]/=2; x2[2*i]/=2; x2[2*i] += (num[t] * (num[t] - 1)/2); } if (m==2){ printf("%lld\n",n*(n-1)/2-ans[0]); } else{ for (long long i = 1; i<m ; i++){ ans[quick_s(root,i,m)] = x2[i]+ x2[m-1+i]; } for (int i = 1; i<m ; i++){ printf("%lld\n",ans[i]); } } } return 0; }
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