# What Is Binary Tree ADT in Data Structure?

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Heather Bennett

What Is Binary Tree ADT in Data Structure?

A binary tree is a fundamental data structure in computer science that is used to represent hierarchical relationships between elements. It consists of a collection of nodes, where each node has at most two children, referred to as the left child and the right child. The topmost node of the tree is called the root.

## Properties of Binary Trees

Binary trees have some important properties that make them useful for various applications:

• Root: The root node is the topmost node in a binary tree and serves as the entry point for accessing other nodes.
• Parent and Children: Each node can have at most two children, referred to as the left child and the right child. Conversely, each non-root node has a parent.
• Leaf Nodes: Leaf nodes are nodes that do not have any children.

They are also known as terminal or external nodes.

• Internal Nodes: Internal nodes are nodes that have at least one child. They are also known as non-terminal or non-leaf nodes.

## Types of Binary Trees

Binary trees can be categorized into different types based on their structural properties:

### Full Binary Tree

A full binary tree is a binary tree where all internal nodes have exactly two children, and all leaf nodes are at the same level. In other words, every node in a full binary tree either has zero children (leaf) or two children.

### Complete Binary Tree

A complete binary tree is a binary tree where all levels except possibly the last level are completely filled, and all nodes are as far left as possible. In a complete binary tree, if a node has an index ‘i’, its left child is at index ‘2i’ and its right child is at index ‘2i + 1’.

### Perfect Binary Tree

A perfect binary tree is a binary tree where all internal nodes have exactly two children, and all leaf nodes are at the same level. Additionally, all levels of the tree are completely filled. In other words, every node in a perfect binary tree either has zero children (leaf) or two children.

## Operations on Binary Trees

Binary trees support several essential operations:

• Insertion: Inserting a new node into the binary tree while maintaining the proper ordering of elements.
• Deletion: Removing a specific node from the binary tree while rearranging the remaining nodes.
• Traversal: Visiting each node in the binary tree in a specific order to perform tasks such as searching for an element or printing the values of nodes.

### Traversal Techniques

There are three commonly used traversal techniques for exploring nodes in a binary tree:

1. Inorder Traversal: In this traversal, we first visit the left subtree recursively, then visit the root node, and finally visit the right subtree recursively.
2. Preorder Traversal: In this traversal, we first visit the root node, then visit the left subtree recursively, and finally visit the right subtree recursively.
3. Postorder Traversal: In this traversal, we first visit the left subtree recursively, then visit the right subtree recursively, and finally visit the root node.

## Applications of Binary Trees

Binary trees have various applications in computer science, including:

• Binary Search Trees (BST): Binary search trees are binary trees that maintain a specific ordering property. They are commonly used for efficient searching, insertion, and deletion operations.
• Expression Trees: Expression trees are binary trees used to represent arithmetic expressions. They can be evaluated to obtain the result of the expression.
• Huffman Coding: Huffman coding is a data compression algorithm that uses binary trees to assign shorter codes to frequently occurring characters or symbols.
• Decision Trees: Decision trees are used in machine learning and artificial intelligence for making decisions based on input features.

In conclusion, a binary tree is a versatile data structure that allows for efficient representation and manipulation of hierarchical relationships. Understanding its properties, types, operations, traversal techniques, and applications is crucial for any programmer or computer science enthusiast.