I am not OP but I definitely have been in similar circumstances where an algorithm became slightly more complex when adding a hash map to cover performance issues with a list.
A trivial example, I recall about 1 month ago calling it out on a Javascript code review where someone was doing a `someList.find(x => x === "something")` inside a loop creating O(n^2) complexity. Rather than change the entire codebase wherever `someList` is used into a new type it is often easier just to suggest we build a Set (linear on length of `someList`) before the loop and use that for lookups within the loop (constant).
Of course, I am talking about circumstances clearly outside of your original model of OPs description. I am tracking more things (the new Set). However, I realize that to give the full context as to why the type of `someList` from my trivial example _couldn't_ be changed easily and why creating a new Set was the most prudent option would require a comment even longer than this essay. So I give OP the benefit of the doubt that he was in a similar situation where using the hashmap everywhere was either difficult or impossible.
A trivial example, I recall about 1 month ago calling it out on a Javascript code review where someone was doing a `someList.find(x => x === "something")` inside a loop creating O(n^2) complexity. Rather than change the entire codebase wherever `someList` is used into a new type it is often easier just to suggest we build a Set (linear on length of `someList`) before the loop and use that for lookups within the loop (constant).
Of course, I am talking about circumstances clearly outside of your original model of OPs description. I am tracking more things (the new Set). However, I realize that to give the full context as to why the type of `someList` from my trivial example _couldn't_ be changed easily and why creating a new Set was the most prudent option would require a comment even longer than this essay. So I give OP the benefit of the doubt that he was in a similar situation where using the hashmap everywhere was either difficult or impossible.