How Do You Represent a Tree in Data Structure?


Larry Thompson

How Do You Represent a Tree in Data Structure?

A tree is a type of data structure that represents a hierarchical structure consisting of nodes connected by edges. It is widely used in computer science and has various applications, such as representing the hierarchical relationships between elements or organizing data in a way that allows for efficient searching and retrieval.

Nodes and Edges

In a tree, each node represents an element, and the edges represent the connections between the nodes. The topmost node is called the root, and it is the starting point of the tree.

Every node in the tree, except for the root, has exactly one parent node, and zero or more child nodes.

Types of Trees

There are several types of trees, each with its own characteristics and use cases. Some common types include:

  • Binary Tree: A binary tree is a type of tree where each node has at most two child nodes – a left child and a right child.
  • Binary Search Tree: A binary search tree (BST) is a special type of binary tree where the values in the left subtree are less than or equal to the parent node’s value, and the values in the right subtree are greater than or equal to the parent node’s value.
  • Balanced Tree: A balanced tree is a type of tree where all leaf nodes are at approximately the same level. This ensures efficient searching and insertion operations.
  • Trie: A trie (also known as prefix tree) is a specialized type of tree used for efficient retrieval of keys that share a common prefix.

Tree Representation

There are several ways to represent a tree in data structure. The most common representation is using linked nodes. In this representation, each node contains a value and references to its child nodes.

The root node represents the entire tree. The child nodes can be stored as an array, linked list, or any other suitable data structure depending on the requirements.

Another way to represent a tree is through an adjacency list. In this representation, each node is associated with a list of its adjacent nodes.

This representation is commonly used for sparse trees where the number of edges is relatively small compared to the number of nodes.

Traversal Techniques

To process or search for elements in a tree, various traversal techniques can be applied. Some common traversal techniques include:

  • Preorder Traversal: In preorder traversal, each node is visited before its children.
  • Inorder Traversal: In inorder traversal, each node’s left subtree is visited first, then the node itself, and finally its right subtree.
  • Postorder Traversal: In postorder traversal, each node’s children are visited before the node itself.
  • Level-order Traversal: In level-order traversal, nodes are visited level by level from left to right.


Representing a tree in data structure involves organizing nodes and edges in a hierarchical manner. Various types of trees exist based on their characteristics and use cases. Trees can be represented using linked nodes or adjacency lists.

Traversal techniques help in accessing and processing elements within a tree. Understanding how to represent and traverse trees is essential for effectively working with hierarchical data structures.

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