Programs that utilize tree strucutres need to process nodes[?] in a tree (represented as circles in below diagram). Nodes contain information about an object. For now, let's assume each node contains a letter. The arrows indicate a link between nodes.
InOrder Traversal is a type of tree traversal[?] algorithm. Inorder refers to when the root is processed inbetween to its two subtrees.
Steps to Inorder Traversal
Given a non-empty tree,
- Process the nodes in the left subtree with a recursive call
- Process the root
- Process the nodes in the right subtree with a recursive call
Given a binary tree PY:
The order would go D,B,G,E,A,C,F
Here is an example of InOrder in C++
template <class Item>
int inorder_print(const binary_tree_nodes<Item>* ptr)
// ptr is a pointer to a node in a binary tree OR null
// meaning empty tree.
{
if (ptr != NULL)
{
inorder_print( ptr->left() );
std::cout << ptr->data() << std::endl;
inorder_print( ptr->right() );
}
return 0;
}
The same example in Haskell might look like
data Tree a = ET | Node(a, Tree a, Tree a)
inorder :: Tree a -> [a] inorder ET = [] inorder (Node (x, left,right)) = (inorder left) ++ [x] ++ (inorder right)
Compare: Pre-order traversal, post-order traversal