哈希表，其中键是字符串，值是c ++中的函数

Question

Is it possible to have an implementation for hash, where key is String and value is function . For the background, I have a program where there is lots of string comparison, ie

if(strcasecmp(s,"london")==0) 
   functionA();  
else if(strcasecmp(s,"moscow")==0)
   functionB();  
else if(strcasecmp(s,"delhi")==0)  
   functionC();  
  ...  

and so on.

But this kind of implementation is very costly (theta(n)) , since String comparison is done for all the if statements. If we have an hash implementation where key is String and value is function , we can just call something like

function = hash.Get("moscow");    
function(); 

Its complexity is good (theta(log(1))) .

Is it possible to do this?

Answer 1

Is it possible to have an implementation for hash, where key is String and value is function?

Yes. This is perfectly feasible. You can use pointers to function or std::function . Possible containers might be:

1. std::unordered_map
2. boost::unordered_map