Efficient Cartesian Product algorithm

Question

Can somebody please demonstrate for me a more efficient Cartesian product algorithm than the one I am using currently (assuming there is one). I\'ve looked around SO and go

Answer 1

The complexity of cartesian product is O(n²), there is no shortcut.

In specific cases, the order you iterate your two axis is important. For example, if your code is visiting every slot in an array — or every pixel in an in image — then you should try to visit the slots in natural order. An image is typically laid out in ‘scanlines’, so the pixels on any Y are adjacent. Therefore, you should iterate over the Y on the outer loop and the X on the inner.

Whether you need the cartesian product or wherther is a more efficient algorithm depends on the problem you are solving.