[bluGill]

> use a map/dictionary instead of an array for key-based access? Nope. That is just correct.

Maybe, maybe not. While the map/dictionary is easier to use, if the number of items is small (which it often is) the array will be substantially faster because the CPU will pre-fetch the next element into the cache while you are still checking if the current one is the right key. Maybe - check with a cache aware profiler, and you need to design your array to be cache friendly.

Of course the above assumes your map/dictionary is on the hot path (seems unlikely), your code is too slow (probably subjectively, but in some real time applications this can be objectively measured), and you are writing in an efficient language. IF All of the above are true, only then should you go to the complexity of using an array to do the job of a map/dictionary.

[noisy_boy]

Also depends on expected changes to the no. of items. If you think it can shoot up, then you are better served by sticking to map/dictionary (and paying the minor penalty, assuming not in hot path) compared to starting with array for low-volume and then having to make code changes to map/dictionary to handle increased volume.