负折叠卷积ntt变换

#include<iostream>
#include<vector>
using namespace std;
class Ntt {
    
    
public:
	int p;
	int w;
	int n;
	vector<int> arrw;
	vector<int> revw;
	Ntt(int p, int w, int n):p(p),w(w),n(n) {
    
    
		
		arrw.resize(1<< n);
		arrw[0] = 1;
		for (int i = 1; i < (1<<n); i++) {
    
    
			arrw[i] = arrw[i - 1] * w % p;
		}
		revw.resize(1 << n );
		revw[0] = 0;
		for (int i = 0; i <= (1<<(n-1)); i++)
			revw[i] = (revw[i >> 1] >> 1) | ((i & 1) << (n - 2));
	}

	vector<int> ntt(vector<int> a) {
    
    
		int k = 0;
		for (int mid = (1<<(n-2)); mid > 0; mid>>=1) {
    
    
			
			for (int start = 0; start < (1<<(n-1)); start+=mid*2) {
    
    
				int wk = arrw[revw[++k]];
				for (int pos = start; pos < start + mid; pos++) {
    
    
					int l = a[pos];
					int r = a[pos + mid] * wk % p;
					
					a[pos] = (l + r) % p;
					a[pos + mid] = (l - r) % p;
					if (a[pos] < 0)a[pos] += p;
					if (a[pos + mid] < 0)a[pos+mid] += p;
					cout << wk << endl;
					for (auto i : a)cout << i << ' ';
					cout << endl << endl;
				}
			}

		}
		
		return a;
	}
	vector<int> rntt(vector<int> a) {
    
    
		int k = (1<<(n-1));
		for (int mid = 1; mid <= (1 << (n - 2)); mid <<= 1) {
    
    
			for (int start = (1 << (n - 1)) - mid*2; start >= 0; start -= mid * 2) {
    
    
				int wk = arrw[((1<<n))-revw[--k]];
				for (int pos = start; pos<start+mid; pos++) {
    
    
					//cout <<"start: "<<start<<" pos: "<< pos << " mid: " << mid << endl;
					int add = (a[pos] + a[pos + mid]) % p ;
					int minus = (a[pos] - a[pos + mid])*wk % p ;
					if (add < 0)add += p;
					if (minus < 0)minus += p;
					if (add % 2)add += p;
					a[pos] = add/2;
					if (minus % 2)minus += p;
					a[pos + mid] = minus/2;

					cout << wk << endl;
					for (auto i : a)cout << i << ' ';
					cout << endl << endl;
				}
			}

		}

		return a;
	}
	
};
int main() {
    
    
	Ntt tmp(17, 2, 3);
	auto vec=tmp.rntt(tmp.ntt({
    
    1,4,3,13}));
	for (auto i : vec) {
    
    
		if (i < 0)
			cout << i + 17 << ' ';
		else
		cout << i << ' ';
	}cout << endl;
}