What Is Balanced and Unbalanced Tree in Data Structure?


Larry Thompson

A balanced tree and an unbalanced tree are two different types of trees used in data structures. Understanding the differences between the two is important for efficient data storage and retrieval.

What is a Tree?

A tree is a hierarchical data structure that consists of nodes connected by edges. Each node in a tree can have zero or more children, except for the root node which has no parent. Trees are commonly used to represent hierarchical relationships between objects or to organize data in a structured manner.

What is a Balanced Tree?

A balanced tree, also known as a height-balanced tree, is a type of binary search tree where the difference in height between the left and right subtrees of any node is at most one. In other words, the heights of the left and right subtrees differ by at most one level.


  • AVL Tree:

    • AVL trees are one of the most commonly used balanced trees.
    • They ensure that the heights of left and right subtrees differ by at most one.
    • This balance property allows for efficient searching, insertion, and deletion operations.

What is an Unbalanced Tree?

An unbalanced tree refers to any binary search tree that does not meet the criteria of being balanced. In an unbalanced tree, there can be a significant difference in height between the left and right subtrees of a node.

  • Binary Search Tree:

    • A binary search tree is an unbalanced tree if the values are inserted in a sorted or nearly sorted order.
    • In such a case, the tree can become heavily skewed to one side, resulting in poor performance for searching and other operations.
    • However, with random or evenly distributed data, a binary search tree can be balanced.

Benefits of Balanced Trees

Using balanced trees offers several benefits:

  • Efficient searching: The height-balanced property of balanced trees ensures that the time complexity for searching is O(log n), where n is the number of nodes in the tree.
  • Efficient insertion and deletion: Balanced trees maintain their balance during insertion and deletion operations, resulting in better performance compared to unbalanced trees.
  • Optimal data organization: Balanced trees provide an optimal organization of data, which is crucial for applications that require quick access to stored information.


In summary, a balanced tree maintains balance by ensuring that the difference in height between its subtrees is limited. This balance allows for efficient searching, insertion, and deletion operations.

On the other hand, an unbalanced tree lacks this balance and can result in poor performance. Understanding these concepts is essential when implementing data structures that require efficient storage and retrieval of information.

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