There is nothing wrong with O(n). It can be faster than O(1) depending on the size of n and what you're doing (small arrays are usually faster than hashmaps for

There is nothing wrong with O(n). It can be faster than O(1) depending on the size of n and what you're doing (small arrays are usually faster than hashmaps for example). Big-O just tells you how something scales. It doesn't really tell you how fast something is.