nod of two polynoms

#include <iostream>
#include <vector>
typedef long long i64;
using namespace std;

int deconv(vector < i64 > &a, vector < i64 > &b, vector < i64 > &q, vector < i64 > &r, i64 n);
vector<i64> nod (vector<i64> a, vector<i64> b, i64 n);
void to_ring(i64 & x, i64 n);
void printv(vector < i64 > &v);

int main()
{
    vector < i64 > a{1,0,0,0,1,1,1,1,1};
    vector < i64 > b{1,0,1,0,1,1,0,1};
    vector < i64 > q, r;
    auto answer = nod(a, b, 2);
    printv(a);
    printv(b);
    //printv(q);
    //printv(r);
    printv(answer);
}

vector<i64> nod (vector<i64> a, vector<i64> b, i64 n){
    vector<i64> q, r;
    deconv(a, b, q, r, n);
    do {
        a = b;
        b = r;
        deconv (a, b, q, r, n);
    } while (r.front() != 0);
    return b;
}

void to_ring(i64 & x, i64 n){
    if ( n != 0 ){
    while (x>n) x -= n;
    while (x<0) x+= n;
    }
}

int deconv(vector < i64 > &a, vector < i64 > &b, vector < i64 > &q, vector < i64 > &r, i64 n)
{
    q.clear();
    r = a;
    i64 limit = r.size() - b.size() + 1;
    for (i64 j = 0; j < limit; ++j)
    {
        q.push_back(r[j] / b.front());
        to_ring(q.back(), n);
        for (i64 i = 0; i < b.size(); ++i){
            r[i + j] -= q.back() * b[i];
            to_ring(r[i+j], n);
        }
    }
    i64 i;
    for (i=0; (i<r.size()-1) &&( r[i] == 0);++i);
    r.erase (r.begin(), r.begin()+i);
    return 0;
}

void printv(vector < i64 > &v)
{
  for (auto & i:v)
        cout << i << " ";
    cout << endl;
}