How Trees Are Implemented in Data Structure?


Scott Campbell

When it comes to data structures, trees are an essential concept to understand. Trees are hierarchical data structures that consist of nodes connected by edges. Each node in a tree can have zero or more child nodes, and there is always one node called the root that has no parent.

Tree Terminology

Before diving into how trees are implemented in data structures, let’s familiarize ourselves with some common tree terminology:

  • Node: A fundamental unit of a tree that contains data and points to its child nodes.
  • Root: The topmost node in a tree that has no parent.
  • Parent: A node that has child nodes connected to it.
  • Child: Nodes directly connected to a parent node.
  • Sibling: Nodes that share the same parent.
  • Leaf: Nodes with no children.
  • Depth: The level of a node within the tree hierarchy. The root has a depth of 0.

How Trees Are Implemented?

Trees can be implemented in various ways based on different requirements and use cases. Here are two commonly used implementations:

1. Array-Based Implementation:

In this implementation, an array is used to represent the tree structure. Each index of the array corresponds to a node, and the value at each index represents the data stored in that node. For any given index i:

  • The left child can be found at index (2 * i + 1).
  • The right child can be found at index (2 * i + 2).
  • The parent can be found at index ((i – 1) / 2).

This implementation is straightforward and provides fast access to nodes. However, it requires a fixed amount of memory regardless of the number of nodes in the tree.

2. Linked List-Based Implementation:

In this implementation, each node in the tree is represented by an object or a struct that contains a data field and references to its child nodes. The root node is represented by a pointer or reference to the object.

Each node object typically has two pointers: one pointing to its left child and another pointing to its right child. Additionally, some node objects may also contain a reference to their parent.

This implementation allows for dynamic memory allocation as nodes are created when needed. It is more flexible than the array-based implementation but may require more memory due to additional pointers.

Common Tree Operations

Trees support several operations that allow efficient manipulation and traversal of data. Some common tree operations include:

  • Insertion: Adding a new node to the tree.
  • Deletion: Removing a node from the tree.
  • Search: Finding a specific node within the tree.
  • Traversal: Visiting all nodes in a specific order (e.g., in-order, pre-order, post-order).


Trees are versatile data structures that find applications in various fields such as computer science, mathematics, and biology. Understanding how trees are implemented and their associated operations is essential for efficient problem-solving and algorithm design.

So the next time you encounter a problem that requires organizing hierarchical data, consider using trees as your go-to data structure!

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