What is a binary tree?

A binary tree is a tree data structure in which each node has at most two children: left and right.

Key characteristics:

• Each node has a pointer to a value (data) and pointers to the left and right children (which can be null).
• There is a root node — the top node of the tree, which has no parent.
• Leaves are nodes that have no children.
• Subtrees — each subtree of the root of a binary tree is also a binary tree.

Main types of binary trees:

• Complete binary tree: at every level except possibly the last, all nodes have two children, and all nodes at the last level are shifted to the left.
• Perfect binary tree: all levels are fully filled, and every node (except leaves) has two children.
• Balanced binary tree: the heights of the left and right subtrees of each node differ by no more than 1.

Applications in QA:

• Test hierarchy: organizing test scenarios or test sets in a tree structure for better readability and navigation.
• Data search and sorting: binary search trees are used for quick search, insertion, and deletion of elements (e.g., in performance testing of data operations).
• Data structuring: representing and organizing test data or execution results.

Example of node representation in Python:

class Node:
    def __init__(self, value):
        self.value = value  # Node value
        self.left = None    # Left child
        self.right = None   # Right child