Numbers = 1-5, List = [1,3,4]. How to get back a list [2,5]?

开发者_如何学运维I think that the question title explains itself :) Suppose that i have the the numbers 1,2,3,4 and 5. Now, i have a list [1,3,4].

What is the best way to get back the inverted list ? A list like [2,5] with the missing elements ?

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As simple as

> [1,2,3,4,5] - [1,3,4]
=> [2, 5] 

Documentation here.

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Use the splat operator to create an array from your range of numbers and then subtract out the set

> [*1..5]-[1,3,4]
 => [2, 5]