What Is Disjoint Tree in Data Structure?


Heather Bennett

What Is Disjoint Tree in Data Structure?

Disjoint sets are an essential concept in data structure that deals with partitioning a set into subsets. Each subset is represented by a tree structure, commonly known as a disjoint tree or a disjoint set forest. In this article, we will explore the concept of disjoint trees and understand how they can be used to solve various problems efficiently.

Disjoint Set Operations

A disjoint set supports two fundamental operations:

  • Merge (Union): This operation merges two subsets into one. It takes two elements from different subsets and combines them into a single subset.
  • Find: This operation determines which subset an element belongs to. It returns the representative element of the subset.

The Disjoint Set Data Structure

The disjoint set data structure consists of an array that represents each element as a node, and each node contains a reference to its parent node. The representative element (also known as the root) of each subset points to itself.

Initially, all elements are considered to be in their own subsets, with each element being its own parent.

Merge (Union) Operation

The merge operation combines two subsets by finding their respective representative elements and making one the parent of the other. The representative element of the resulting subset becomes the new representative element for both original subsets.

Find Operation

The find operation determines which subset an element belongs to by recursively traversing the parent pointers until reaching the representative element (root). The root represents its own subset and is returned as the result of this operation.

Applications of Disjoint Trees

Disjoint trees are widely used in various algorithms and applications. Some of the most common applications include:

  • Connected Components: Disjoint sets can efficiently determine the connected components in a graph by merging subsets that share common elements.
  • Cycle Detection: Disjoint sets can be used to detect cycles in an undirected graph by checking if there is a merge operation between two elements that already belong to the same subset.
  • Kruskal’s Minimum Spanning Tree Algorithm: Disjoint sets play a crucial role in Kruskal’s algorithm to find the minimum spanning tree of a weighted graph.


In conclusion, disjoint trees are a powerful data structure that allows for efficient partitioning of sets into subsets. They support merge and find operations, which enable various applications such as finding connected components and detecting cycles. Understanding and implementing disjoint trees can greatly enhance your problem-solving skills in data structures and algorithms.

Now that you have learned about disjoint trees, you can start exploring their implementation and applying them to solve real-world problems.

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