What Is Height Balanced Tree in Data Structure?


Heather Bennett

A height-balanced tree is a type of binary tree in data structure where the difference in the height of the left and right subtrees is at most one. This property ensures that the tree remains balanced and guarantees efficient operations such as searching, insertion, and deletion.

Why is Tree Balancing Important?

Tree balancing is important because it ensures that all operations on the tree have a time complexity of O(log n), where n is the number of elements in the tree. Without balancing, the height of the tree can become skewed, resulting in degraded performance with time complexity approaching O(n) for certain operations.

How Does a Height-Balanced Tree Work?

A height-balanced tree maintains balance by dynamically adjusting its structure during insertions and deletions. The most common implementation of a height-balanced tree is an AVL (Adelson-Velsky and Landis) tree or a red-black tree.

AVL Tree

An AVL tree is a self-balancing binary search tree where each node contains an extra attribute called balance factor. The balance factor represents the difference between the heights of the left and right subtrees.

  • If balance factor = -1: The left subtree is taller by one level.
  • If balance factor = 0: The left and right subtrees are equally tall.
  • If balance factor = 1: The right subtree is taller by one level.

To maintain balance, AVL trees perform rotations when necessary. A rotation involves rearranging nodes to preserve their order while reducing or eliminating any imbalance in heights.

Red-Black Tree

A red-black tree is another type of self-balancing binary search tree. It maintains balance by enforcing five properties:

  1. Every node is either red or black.
  2. The root and leaves (null nodes) are black.
  3. If a node is red, both its children are black.
  4. Every path from a node to its null descendant contains the same number of black nodes.
  5. The maximum depth of a leaf node is at most twice the minimum depth of any leaf node (also known as the “black height” property).

By adhering to these properties, red-black trees ensure that the longest path from the root to any leaf is no more than twice as long as the shortest path. This guarantees a height-balanced structure and efficient operations.

Benefits of Height-Balanced Trees

Height-balanced trees offer several benefits:

  • Efficient Operations: With their balanced structure, height-balanced trees provide efficient search, insertion, and deletion operations with a time complexity of O(log n).
  • Predictable Performance: Unlike unbalanced binary trees, height-balanced trees maintain consistent performance regardless of the order in which elements are inserted or deleted.
  • Optimal Memory Usage: The memory usage of height-balanced trees is optimized due to their balanced nature. This ensures that memory allocations are proportional to the number of elements in the tree.

In Conclusion

A height-balanced tree plays a crucial role in maintaining efficiency and predictable performance in various data structure operations. By ensuring that the heights of left and right subtrees differ by at most one level, operations on such trees can be performed with optimal time complexity.

AVL trees and red-black trees are popular implementations of height-balanced trees, each with its own set of balancing strategies. Understanding and utilizing height-balanced trees can greatly enhance the performance of applications that involve heavy data processing and retrieval.

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