Very readable and logical. Oh, this language design...

Can you explain how this is inefficient. Would be helpful for me.

Agree with all of the comments. I eliminated the fullName field only to find out the tests verify its existence and public accessibility. Why?!

Okay, wow, that's amazing

to baybass the case sensitivity for example(a,A) we will convert them first to upper (A,A) and then compare

Actually, BigInteger is not allowed.

why do we need to converting it to upper case?

Respect++

I think in question it is specifically mentioned that hashcode & equals contract has been already taken care of So no need to worry about that key collision. But still yes to be on more safer side we can use this Identity hashmap.

nice

If we make a concatenation of string is better to declare a "std::stringstream" instead of "std::string"?!?

Why?

Thank you for sharing the tip with the IdentityHashMap. I did not know about IdentityHashMap. That's why I used a LinkedList and the '==' operator. I didn't realized that I also could put the object identity to a map :-D