I'm beginning to study algorithmic stuff, and I'm confused about the notation O(n + m). I've seen some people take that to mean it's the maximum between 'n' and 'm', so O(max(n,m)) and others who read it literally. So if p = n + m, it'd be like saying O(p).
Which one is correct? Does it vary or is it standardized rule when talking about algorithms? Thanks!