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copied!<p>Here's a variant without nested loops. I've tried to use a similar to <a href="https://stackoverflow.com/questions/327531/can-i-optimize-code-that-has-3-for-loops-and-4-ifs">your question</a> notation.</p> <pre><code>// g++ 26neighbours.cpp -o 26neighbours && 26neighbours #include <algorithm> #include <iostream> #include <iterator> #include <vector> namespace { struct Pos { double x, y, z; template<class Char, class Traits> friend std::basic_ostream<Char, Traits>& operator<< (std::basic_ostream<Char, Traits>& out, const Pos& p) { return out << p.x << " " << p.y << " " << p.z; } explicit Pos(double x_ = 0, double y_ = 0, double z_ = 0) : x(x_), y(y_), z(z_) { } }; template <class OutputPosIterator, class InputPosIterator, class Number> void translate(OutputPosIterator first, OutputPosIterator last, InputPosIterator delta, Number factor) { for ( ; first != last; ++first, ++delta) { first->x += delta->x * factor; first->y += delta->y * factor; first->z += delta->z * factor; } } } int main(int argc, char *argv[]) { const Pos delta[] = { // ruby -e"(-1..1).each{|i| (-1..1).each{|j| (-1..1).each{|k| printf(\"Pos(%2d,%2d,%2d),\n\", i, j, k) if (i!=0 || j!=0 || k!=0)}}}" Pos(-1,-1,-1), Pos(-1,-1, 0), Pos(-1,-1, 1), Pos(-1, 0,-1), Pos(-1, 0, 0), Pos(-1, 0, 1), Pos(-1, 1,-1), Pos(-1, 1, 0), Pos(-1, 1, 1), Pos( 0,-1,-1), Pos( 0,-1, 0), Pos( 0,-1, 1), Pos( 0, 0,-1), Pos( 0, 0, 1), Pos( 0, 1,-1), Pos( 0, 1, 0), Pos( 0, 1, 1), Pos( 1,-1,-1), Pos( 1,-1, 0), Pos( 1,-1, 1), Pos( 1, 0,-1), Pos( 1, 0, 0), Pos( 1, 0, 1), Pos( 1, 1,-1), Pos( 1, 1, 0), Pos( 1, 1, 1), }; const int N = sizeof(delta) / sizeof(*delta); // find neighbours of somePos double cube_size = 0.5; Pos somePos(0.5, 0.5, 0.5); std::vector<Pos> neighbours(N, somePos); translate(neighbours.begin(), neighbours.end(), delta, cube_size); // print neighbours std::copy(neighbours.begin(), neighbours.end(), std::ostream_iterator<Pos>(std::cout, "\n")); std::cout << std::endl; return 0; } </code></pre>

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