Trees

In the world of data structures, a tree is a hierarchical structure that consists of nodes connected by edges. It is a non-linear data structure that represents a set of elements hierarchically.

Basic Terminology

To understand trees, it's important to be familiar with some basic terminology:

1. Node: Each element in a tree is called a node. Each node contains a value and may have zero or more child nodes.

2. Parent and Child: In a tree, a node that is connected to another node directly above it is called the parent node, and the node connected to it directly below is called the child node.

3. Root: The topmost node in a tree is called the root node. It has no parent node.

4. Leaf: A node that has no child nodes is called a leaf node or a terminal node.

Traversal Techniques

There are several ways to traverse or visit the nodes in a tree:

1. Pre-order traversal: Visit the root node, then recursively visit the left subtree, and finally recursively visit the right subtree.

2. In-order traversal: Recursively visit the left subtree, then visit the root node, and finally recursively visit the right subtree.

3. Post-order traversal: Recursively visit the left subtree, recursively visit the right subtree, and finally visit the root node.

4. Level-order traversal: Visit the nodes level by level, starting from the root node and moving from left to right at each level.

Java Example

Let's take a look at an example of creating and traversing a simple binary tree using Java:

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