ntt

src/ntt.cpp

+#include "ntt.h"
+
+int NTT::modExp(int base, int power, int mod){
+    int res = 1;
+    int p = power;
+    int b = base % mod;
+    while (p > 0){
+        if (p & 1){
+            res = (res * b) % mod;
+        }
+        b = (b*b) % mod;
+        p = p >> 1;
+    }
+
+    return res;
+}
+
+int NTT::modInv(int x, int mod){
+    int t = 0;
+    int t1 = 1;
+    int r, r1 = mod, x;
+
+    while (r1 != 0){
+        int quot = (int) (r/r1);
+        int temp_t1 = t1;
+        int temp_t = t;
+        int temp_r1 = r1;
+        int temp_r = r;
+        t, t1 = t1, (t - quot * t1);
+        r, r1 = r1, (r % r1);
+    }
+    
+    if (t<0){
+        t = t + mod;
+    }
+    
+    return t;
+}
+
+void NTT::_ntt(vector<int64_t> &in, bool inverse){
+
+}
+
+vector<int64_t> NTT::ntt(Polynomial in){
+    vector<int64_t> out(in.degree,0);
+    _ntt(out, true);
+    return out;
+}
+
+Polynomial NTT::intt(vector<int64_t> in){
+    vector<int64_t> out(size(in),0);
+    Polynomial pOut(size(out));
+    int n_inv = modInv(size(out), M);
+
+    _ntt(out,false);
+    
+    return pOut;
+}
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src/ntt.h

+#include "polynomial.h"
+#include <iostream>
+#include <vector>
+
+using namespace std;
+
+#define size(c) ((int)(c).size())
+
+#ifndef NTT_H
+#define NTT_H
+
+class NTT{
+    public:
+        int g = 3;
+        int M = 998244353;
+        int modExp(int base, int power, int mod);
+        int modInv(int x, int mod);
+        void _ntt(vector<int64_t> &in, bool inverse);
+        vector<int64_t> ntt(Polynomial in);
+        Polynomial intt(vector<int64_t> in);
+};
+
+
+#endif
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