Fastest possible string key lookup for known set of keys

Question

Consider a lookup function with the following signature, which needs to return an integer for a given string key:

int GetValue(string key) { ... }
         


        

Answer 1

What you want is a look-up table of look-up tables. If memory cost is not an issue you can go all out.

const int POSSIBLE_CHARCODES = 256; //256 for ascii //65536 for unicode 16bit
struct LutMap {
    int value;
    LutMap[POSSIBLE_CHARCODES] next;
}
int GetValue(string key) {
    LutMap root = Global.AlreadyCreatedLutMap;
    for(int x=0; x