Switch statement with huge number of cases

Question

What happens if the switch has more than 5000 case. What are the drawbacks and how we can replace it with something faster?

Note: I am not expe

Answer 1

There's no specific reason to think you'd want anything other than a switch/case statement (and indeed I'd actively expect it to be unhelpful). The compiler should create efficient dispatching code, which might involve some combination of static [sparse] table(s) and direct indexing, binary branching etc.; it's got insights into the static values of the cases and should do an excellent job (retuning it on the fly each time you change the cases, whereas new values that don't fit well with a hand-crafted approach - such as wildly differing values when you'd had a pretty packed array lookup - could require reworking of code or silently cause memory bloat or a performance drop).

People really cared about this kind of thing back when C was trying to win over hard-core assembly programmers... the compilers were held accountable for generating good code. Put another way - if it's not (measurably) broken, don't fix it.

More generally, it's great to be curious about this kind of thing and get people's ideas on alternatives and their performance implications, but if you really care and the performance difference could make a useful difference to your program (especially if profiling suggests it) then always benchmark with your program doing real work.