# What Is Indegree in Data Structure?

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Larry Thompson

Indegree is a concept in data structure that is used to determine the number of incoming edges for a vertex in a directed graph. In simple terms, it represents the number of edges that are pointing towards a particular vertex in the graph.

## Understanding Indegree

Indegree is an important property of directed graphs and is often used in various algorithms and applications. It helps in analyzing the flow of data or information within a graph.

In a directed graph, each vertex can have multiple outgoing edges that point to other vertices. These outgoing edges are also known as outdegree. On the other hand, indegree represents the number of edges pointing towards a specific vertex.

### Calculating Indegree

To calculate the indegree of a vertex in a directed graph, we need to count the number of edges that are pointing towards that vertex.

We can iterate through all the vertices in the graph and for each vertex, count the number of incoming edges by checking its adjacent vertices. By doing this for all vertices, we can determine their respective indegrees.

#### Example:

Consider the following directed graph:

```  A → B
↑   ↓
D ← C
```
• The indegree of A is 0 because no edge is pointing towards A.
• The indegree of B is 1 because there is one edge (A → B) pointing towards B.
• The indegree of C is 1 because there is one edge (D → C) pointing towards C.
• The indegree of D is 1 because there is one edge (A → D) pointing towards D.

### Applications of Indegree

Indegree is widely used in various applications and algorithms. Some common applications include:

• Topological sorting: Indegree is used to determine the order of vertices in a directed acyclic graph.
• PageRank algorithm: Indegree is used to calculate the importance or popularity of web pages in a network of hyperlinks.
• Dependency resolution: Indegree is used to resolve dependencies between tasks or modules in a software system.

## Conclusion

In summary, indegree is a concept in data structure that represents the number of incoming edges for a vertex in a directed graph. It helps in analyzing the flow of data within the graph and is used in various applications and algorithms.

By understanding the concept of indegree and its calculation, you can gain insights into the structure and relationships within a directed graph.