Question

I would like to know how a set is implemented in C++. If I were to implement my own set container without using the STL provided container, what would be the best way to go about this task?

I understand STL sets are based on the abstract data structure of a binary search tree. So what is the underlying data structure? An array?

Also, how does insert() work for a set? How does the set check whether an element already exists in it?

I read on wikipedia that another way to implement a set is with a hash table. How would this work?

Answer 1

You could implement a binary search tree by first defining a Node struct:

struct Node
{
  void *nodeData;
  Node *leftChild;
  Node *rightChild;
}

Then, you could define a root of the tree with another Node *rootNode;

The Wikipedia entry on Binary Search Tree has a pretty good example of how to implement an insert method, so I would also recommend checking that out.

In terms of duplicates, they are generally not allowed in sets, so you could either just discard that input, throw an exception, etc, depending on your specification.