Every O(n) is O(1) if n = 1. Complexity measures worst-case by-definition, not all cases.
It has two parameters and depending on their relation it will act differently, it's reasonable to include this information. It is worst case O(1) when n and k don't differ much.
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It has two parameters and depending on their relation it will act differently, it's reasonable to include this information. It is worst case O(1) when n and k don't differ much.