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  1. #include <iostream>
  2. #include <vector>
  3.  
  4. using namespace std;
  5.  
  6. vector<int> poly_mul_naive(const vector<int>& a, const vector<int>& b)
  7. {
  8.   if (a.empty() || b.empty())
  9.   {
  10.     return vector<int>();
  11.   }
  12.   vector<int> ret(a.size() + b.size() - 1, 0);
  13.   for (int ia = 0; ia < a.size(); ia++)
  14.   {
  15.   	for (int ib = 0; ib < b.size(); ib++)
  16.   	{
  17.   		ret[ia + ib] += a[ia] * b[ib];
  18.   	}
  19.   }
  20.   return ret;
  21. }
  22.  
  23. void print_poly(const vector<int>& a)
  24. {
  25.   cout << "[";
  26.   if (!a.empty())
  27.   {
  28.     cout << a[a.size() - 1];
  29.   }
  30.   for (int i = a.size() - 2; i >=0; i--)
  31.   {
  32.   	cout << ", " << a[i];
  33.   }
  34.   cout << "]";
  35. }
  36.  
  37. istream& operator>>(istream& input, vector<int>& v)
  38. {
  39.   v.clear();
  40.   size_t size;
  41.   input >> size;
  42.   v.reserve(size);
  43.   for (size_t i = 0; i < size; i++)
  44.   {
  45.   	int a;
  46.   	input >> a;
  47.   	v.push_back(a);
  48.   }
  49.   return input;
  50. }
  51.  
  52. int main()
  53. {
  54.   vector<int> a;
  55.   cin >> a;
  56.   vector<int> ret(1, 1); // [1]
  57.   vector<int> poly(2, 1); // [1; 1] - drugi (idx: 0) element będziemy zastępywać
  58.   for (int i = 0; i < a.size(); i++)
  59.   {
  60.   	poly[0] = -a[i];
  61.   	ret = poly_mul_naive(ret, poly);
  62.   }
  63.   print_poly(ret);
  64.   return 0;
  65. }
Success #stdin #stdout 0s 3436KB
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stdin
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3
2 -2 1
stdout
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[1, -1, -4, 4]
https://ideone.com/E8MGHF
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
secret

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