gmile gmile - 2 months ago 5x
Ruby Question

Get index of array element faster than O(n)

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

to get it? The problem comes from the need of keeping really huge array and calling
enormous amount of times.

After a couple of tries I found that caching indexes inside elements by storing structs with
(value, index)
fields instead of the value itself gives a huge step in performance (20x times win).

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).


Convert the array into a hash. Then look for the key.

array = ['a', 'b', 'c']
hash = Hash[]    # => {"a"=>0, "b"=>1, "c"=>2}
hash['b'] # => 1