how to point at multiply struct with one struct pointer in c++ - class

Question

Write a assign_obj.h file so that the assign_driver file will output the
following. When implementing assign_obj.h think about how efficient your program will run. You must
implement your assign_obj class using a dynamic array.
assign_obj:: assign_obj() function will just set size to zero
assign_obj:: assign_obj(std::string s) function will go through each character of string and convert it to uppercase and push it the last of A
std::ostream& operator<<(std::ostream & out, assign_obj & obj) function will go through each data in obj.A vector and convert integer into string and
than output the data in this format [value:count value:count ....]
class assign_obj{
private:
struct item{
char value;
int count;
};
item *A;
int size;
public:
assign_obj();
assign_obj(std::string);
friend std::ostream& operator<<(std::ostream & out, assign_obj & obj);
}
int main(){
assign_obj ao1("dsdfdf");
std::cout << ao1 << std::endl;
}
This is the output that I want
[ D:1 S:1 D:1 F:1 D:1 F:1 ]
assign_obj:: assign_obj(){
size = 0;
}
assign_obj:: assign_obj(std::string s){
size = s.size();
for(int i = 0; i < s.size(); i++){
char c = std::toupper(s[i]);
A = new item{c,1};
}
}
# std::ostream& operator<<(std::ostream & out, assign_obj & obj){
std::cout<< "size: " << obj.size <<std::endl;
out << "[ ";
for(int i = 0; i < obj.size; i++){
out << obj.A[i].value << ":" << std::to_string(obj.A[i].count) << " ";
}
out << "]" << "\n";
return out;
}