What Is Empty Graph in Data Structure?


Angela Bailey

In the field of data structures, an empty graph is a graph that does not contain any vertices or edges. It is essentially a blank canvas that can be populated with nodes and connections as needed. Let’s delve deeper into understanding what an empty graph entails and its significance in the context of data structures.

Empty Graph Definition

An empty graph, also known as a null graph, is a fundamental concept in graph theory. It serves as the starting point for constructing more complex graphs by adding vertices and edges. In simple terms, it represents a graph without any nodes or connections.

Empty Graph Properties

An empty graph possesses several defining properties:

  • No Vertices: As mentioned earlier, an empty graph does not have any vertices. These are the fundamental units that represent entities within the graph.
  • No Edges: Similarly, an empty graph lacks edges, which are the connections between pairs of vertices in a graph.
  • Size and Order: The size of an empty graph refers to the number of edges it contains, which is zero in this case. The order of an empty graph denotes the number of vertices it contains, also zero.

Applications of Empty Graphs

While an empty graph may seem trivial at first glance, it plays a crucial role in various aspects of data structures and algorithms. Here are some applications:

Graph Initialization:

When designing algorithms or implementing data structures that involve graphs, initializing with an empty graph is often the first step. It provides a clean slate to build upon and facilitates efficient construction and modification operations.

Detecting Graph Emptiness:

Empty graphs are also useful for checking if a given graph is empty or not. By comparing the number of vertices and edges, one can easily determine if the graph is devoid of any nodes or connections.

Graph Algorithms:

Many graph algorithms, such as breadth-first search (BFS) and depth-first search (DFS), are designed to operate on both empty and non-empty graphs. Starting with an empty graph allows these algorithms to be adapted for various scenarios without any assumptions about the initial state of the graph.


In summary, an empty graph serves as the foundation for constructing more complex graphs. It represents a graph without any vertices or edges and possesses unique properties that make it valuable in various applications. Whether initializing a new graph or checking for emptiness, understanding the concept of an empty graph is crucial in the field of data structures.

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