Iterator Design Pattern

• An iterator is an object that facilitates the traversal of a data structure

  • It keeps a ref to the current element

  • Knows how to move to a different element

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    Ex. Above are inbuilt C++ forward and reverse iterators. You can also get constant iterators using crbegin()

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  • In C++ the range-based for-loop has no reverse iterator

Building an iterator for a Binary Tree

• Let us define a BinaryTree Node class of generalised key value

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  Similarly, let's define a class BinaryTree which maintains our Binary Tree

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  Now we we will build a Pre-order iterator for this tree (Node->Left->Right)

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  We can also set this as the default iterator for our BinaryTree class

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  Now to finally create a tree, we can do something like the below

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