What Is Rooted Tree in Data Structure?


Scott Campbell

A rooted tree is a fundamental data structure in computer science and is widely used in various applications such as hierarchical data representation, graph algorithms, and file systems. In this article, we will explore the concept of a rooted tree and its key properties.

What is a Rooted Tree?

A rooted tree is a directed acyclic graph (DAG) where one node is designated as the root. The root node has no incoming edges, while all other nodes have exactly one incoming edge. Each node in the tree can have zero or more child nodes, forming a hierarchical structure.

Key Properties of a Rooted Tree

A rooted tree exhibits several important properties:

  • Root: The root node is the starting point of the tree and serves as the entry point for accessing all other nodes in the structure.
  • Parent and Child: Each non-root node has a unique parent node, which is the node directly above it. Conversely, each non-leaf node can have multiple child nodes.
  • Ancestor and Descendant: An ancestor of a given node is any node that lies on its path to the root. Conversely, a descendant of a given node is any node that can be reached by following paths downward from that specific node.
  • Leaf Nodes: Leaf nodes are the terminal nodes of the tree that do not have any child nodes.

    They are also referred to as external nodes or leaves.

  • Internal Nodes: Internal nodes are all non-leaf nodes in the tree that have at least one child. They represent intermediate stages between the root and leaf nodes.
  • Depth: The depth of a node in a rooted tree is the number of edges from the root to that node.
  • Height: The height of a rooted tree is the maximum depth among all its nodes. It represents the longest path from the root to a leaf node.

Applications of Rooted Trees

The concept of rooted trees has diverse applications in computer science and beyond. Some common applications include:

Hierarchical Data Representation

Rooted trees are excellent for representing hierarchical data structures such as organization charts, family trees, and file systems. In these scenarios, each node represents an entity, and the parent-child relationship reflects the hierarchical structure.

Graph Algorithms

Rooted trees play a crucial role in graph algorithms like depth-first search (DFS) and breadth-first search (BFS). They enable efficient traversal and exploration of graphs by organizing nodes into a structured hierarchy.

File Systems

In file systems, directories can be organized as rooted trees. Each directory acts as an internal node, while files act as leaf nodes. This structure allows for easy navigation and management of files and directories.


In conclusion, a rooted tree is a powerful data structure that provides an organized way to represent hierarchical relationships. Its properties such as root, parent-child relationship, ancestors, descendants, leaves, depth, and height make it valuable in various applications like hierarchical data representation, graph algorithms, and file systems. By understanding the concept of rooted trees and their applications, you can enhance your problem-solving skills in computer science and related fields.

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