#include <iostream>
 
 
constexpr std::size_t hash(char const* const str) {
   return str[0];
}
 
 
int main() {
   constexpr char const* ids[] = {
         "a"
       , "b"
       , "c"
   };
 
   char const* string = "a";
 
   switch (hash(string)) {
   case hash(ids[0]):
      std::cout << ids[0] << std::endl;
      break;
   case hash(ids[1]):
      std::cout << ids[1] << std::endl;
      break;
   case hash(ids[2]):
      std::cout << ids[2] << std::endl;
      break;
   default:
      std::cout << "default" << std::endl;      
   }
}

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