Get index of array element faster than O(n)

Question

Given I have a HUGE array, and a value from it. I want to get index of the value in array. Is there any other way, rather then call Array#index to get it? The p

Answer 1

Still I wonder if there's a more convenient way of finding index of en element without caching (or there's a good caching technique that will boost up the performance).

You can use binary search (if your array is ordered and the values you store in the array are comparable in some way). For that to work you need to be able to tell the binary search whether it should be looking "to the left" or "to the right" of the current element. But I believe there is nothing wrong with storing the index at insertion time and then using it if you are getting the element from the same array.