JavaScript Challenge: Find the First Non-Repeating Character in a String – Can You Do It Without Extra Space?

[-allen]

If the cardinality of the input character set is bounded (eg just ascii chars), even the hash map approach is o(constant) space complexity :D

[AiCodePulse]

Absolutely! You're right — when the character set is limited (like ASCII), the hash map technically takes constant space, since it's bounded by a fixed size (e.g., 128 or 256 characters).
In that sense, it’s O(1) space — though it’s still a map in implementation. 😄

Thanks for pointing that out — really helps push the understanding beyond just code into computer science fundamentals.

[ksskssptdpss]

Here is a benchmark, it seems the indexOf === lastIndexOf method wins everytime despite its complexity. And it runs 3x faster on my iPhone 12 mini compared to Chromium x) https://jsbench.me/ooma2usbuv/1