// [[Rcpp::export]]IntegerVectormatchCpp( CharacterVector x, CharacterVector table){// first train an unordered_map  std::unordered_map<String,int> map ;for(int i=0; i<table.size(); i++){    String s = table[i] ;    map[s] = i +1 ;  }// now lookupint n = x.size() ;  IntegerVectorout(n) ;for(int i=0; i<n; i++){    String s = x[i] ;    out[i] = map[s]->second ;  }return out ;}