Final answer:
Pre-order traversal is a method of visiting each node in a tree by processing the current node before its children. A node is traversed in the 'Visit-Left-Right' order, and its complexity is O(n), meaning each node is visited once.
Step-by-step explanation:
The pre-order traversal of a tree is a depth-first traversal strategy where each node is processed before its children. The pre-order pattern follows the 'Visit-Left-Right' methodology, which means that the current node is visited first, and then the left subtree is traversed, followed by the right subtree. The recursive nature of this operation ensures that each subtree is also traversed in pre-order.
Here is a pseudocode example of pre-order traversal:
PROCEDURE preOrder(node)
IF node == NULL
RETURN
PRINT node.value
preOrder(node.left)
preOrder(node.right)
END PROCEDURE
The running time of pre-order traversal on a binary tree is O(n), where n is the number of nodes in the tree. This efficiency is because each node is visited exactly once during the traversal.