Which kind of data organization using C arrays makes fastest code and why?

Question

Given following data, what is the best way to organize an array of elements so that the fastest random access will be possible?

Each element has some int number,

Answer 1

Impossible to say. As with any performance related test, the answer my vary by any one or more of your OS, your CPU, your memory, your compiler etc.

So you need to test for yourself. Set your performance targets, measure, optimise, repeat.