What Are Trees and Graphs in Data Structure?


Angela Bailey

When it comes to data structures, two commonly used and closely related concepts are trees and graphs. These structures play a crucial role in organizing and representing data in various applications. In this article, we will explore what trees and graphs are, how they differ from each other, and their significance in computer science.


A tree is a hierarchical data structure that consists of nodes connected by edges. It is similar to the structure of a real-life tree with branches and leaves.

In a tree, there is always a single node called the root, which serves as the starting point. Each node in the tree can have zero or more child nodes.

Types of Trees:

There are different types of trees based on their properties and relationships among nodes:

  • Binary Tree: A binary tree is a type of tree where each node can have at most two child nodes, known as the left child and the right child.
  • Binary Search Tree (BST): A binary search tree is a type of binary tree where the value of each node in the left subtree is lesser than its parent node, and the value of each node in the right subtree is greater than its parent node.
  • Balanced Tree: A balanced tree is a type of tree where the height difference between its left and right subtrees is minimal. Examples include AVL trees and Red-Black trees.
  • B-Tree: B-trees are self-balancing search trees that can handle large amounts of data efficiently by keeping multiple keys per node.


A graph is a non-linear data structure that consists of a set of vertices (also known as nodes) connected by edges. Unlike trees, graphs can have cycles and can be disconnected. Graphs are widely used to represent relationships between objects or entities.

Types of Graphs:

There are different types of graphs based on their properties and connections:

  • Undirected Graph: An undirected graph is a graph where edges have no direction. It represents symmetric relationships between vertices.
  • Directed Graph (Digraph): A directed graph is a graph where edges have a specific direction.

    It represents asymmetric relationships between vertices.

  • Weighted Graph: A weighted graph is a graph where edges have weights or costs associated with them. It is used to represent scenarios where the edges between vertices have some value or significance.
  • Cyclic Graph: A cyclic graph is a graph that contains at least one cycle, allowing you to traverse through the vertices and return to the starting point.

In summary, trees and graphs are fundamental data structures that provide efficient ways to store and organize data. While trees follow a hierarchical structure with a single root node, graphs allow for more complex relationships between nodes with cycles and potentially disconnected components. Understanding these structures is crucial for solving various problems in computer science and software development.

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