What Is Disjoint Set Data Structure Operations?


Larry Thompson

The Disjoint Set Data Structure, also known as the Union-Find Data Structure, is a fundamental concept in computer science and is widely used in various algorithms and applications. It is primarily used to efficiently manage a partition of a set into disjoint subsets.



The MakeSet operation creates a new set with a single element x. It initializes the set’s unique representative pointer to itself.


The Find operation determines the representative of the set that x belongs to. It returns the representative element of the set containing x.

Union(x, y)

The Union operation merges two sets together by connecting their representatives. It takes two elements x and y as input and combines the sets containing these elements into a single set.


To implement the Disjoint Set Data Structure, we can use an array or a linked list-based representation. Each element in the structure represents a node, and its index or reference points to its parent or representative.

Making Sets:

To create a new set, we initialize each element with its own parent pointer pointing to itself. This means that initially, each element is its own representative.

Finding Representatives:

To find the representative of an element x, we follow its parent pointers until we reach an element whose parent pointer points to itself. This element is the representative of its corresponding set.

Union Operation:

To merge two sets containing elements x and y, we find their respective representatives using Find operations. If they are already part of the same set (i.e., their representatives are equal), no further action is required. Otherwise, we make one representative point to another by updating their parent pointers.


The Disjoint Set Data Structure is used in a wide range of algorithms and applications, including:

  • Graph Algorithms: It is used to detect cycles and find connected components in a graph efficiently.
  • Maze Generation and Image Processing: It can be used to create mazes and perform image segmentation tasks.
  • Kruskal’s Minimum Spanning Tree Algorithm: It utilizes the Union-Find Data Structure to efficiently determine the minimum spanning tree of a graph.
  • Network Connectivity: It helps in determining whether two nodes are connected in a network or not.


The Disjoint Set Data Structure is a powerful tool in computer science that allows efficient management of partitioned sets. Its operations, including MakeSet, Find, and Union, provide the necessary tools for effectively merging and querying disjoint sets. By understanding its implementation and applications, you can leverage it to solve various problems efficiently.

Implementing the Disjoint Set Data Structure effectively requires a solid understanding of its operations and their complexities. With practice, you will become proficient in utilizing this data structure to solve complex problems in computer science.

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