Algorithm to determine if array contains n…n+m?

Question

I saw this question on Reddit, and there were no positive solutions presented, and I thought it would be a perfect question to ask here. This was in a thread about interview

Answer 1

Why do the other solutions use a summation of every value? I think this is risky, because when you add together O(n) items into one number, you're technically using more than O(1) space.

O(1) indicates constant space which does not change by the number of n. It does not matter if it is 1 or 2 variables as long as it is a constant number. Why are you saying it is more than O(1) space? If you are calculating the sum of n numbers by accumulating it in a temporary variable, you would be using exactly 1 variable anyway.

Commenting in an answer because the system does not allow me to write comments yet.

Update (in reply to comments): in this answer i meant O(1) space wherever "space" or "time" was omitted. The quoted text is a part of an earlier answer to which this is a reply to.