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#include <algorithm>
#include <vector>
#include <iterator>
#include <iostream>
using namespace std;
class NaturalSquares
{
size_t d_newsqr;
size_t d_last;
public:
NaturalSquares(): d_newsqr(0), d_last(0)
{}
size_t operator()()
{ // using: (a + 1)^2 == a^2 + 2*a + 1
return d_newsqr += (d_last++ << 1) + 1;
}
};
int main()
{
vector<size_t> uv(10);
generate_n(uv.begin(), 5, NaturalSquares{});
copy(uv.begin(), uv.end(), ostream_iterator<int>{ cout, " " });
cout << '\n';
}
// Displays: 1 4 9 16 25 0 0 0 0 0
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