### Topological Sort vs Depth-First Search (DFS)

In this post, we will learn the difference between Topological Sort and Depth-First Search (DFS) in Java. This is a frequently asked question in Java interviews for beginners. Let's dive into it.

## Difference between Topological Sort and Depth-First Search (DFS) in Java

FeatureTopological SortDepth-First Search (DFS)
PurposeTopological Sort is used to find a linear ordering of vertices in a directed acyclic graph (DAG) such that for every directed edge (u, v), vertex u comes before vertex v in the ordering.DFS is a graph traversal algorithm used to visit all the vertices and edges of a graph, exploring as far as possible along each branch before backtracking. It is used to explore and analyze the structure of the graph.
Graph TypeTopological Sort is applicable only for Directed Acyclic Graphs (DAGs) because it requires a linear ordering.DFS can be applied to both directed and undirected graphs, including cyclic graphs. It can handle both connected and disconnected graphs.
Algorithm ComplexityThe time complexity of the Topological Sort is O(V + E), where V is the number of vertices and E is the number of edges in the graph.The time complexity of DFS is also O(V + E), where V is the number of vertices and E is the number of edges in the graph.
Order of VisitingIn Topological Sort, vertices are visited in a specific order such that all the prerequisites of a vertex are visited before the vertex itself.In DFS, the order of visiting vertices is determined by the order of exploration along each branch. It may not follow any specific order.
Cycle DetectionTopological Sort can detect cycles in a graph. If the graph contains cycles, it is not possible to perform a valid topological sort.DFS can also be used to detect cycles in a graph. When a back edge (an edge to an ancestor in the DFS traversal) is encountered, a cycle is detected.
ApplicationTopological Sort is commonly used in tasks that have dependencies, such as task scheduling, build systems and job scheduling.DFS is used in various graph-related algorithms, such as finding connected components, detecting cycles, topological ordering, and solving graph traversal problems.
Dependency ManagementTopological Sort can help identify tasks with dependencies and determine the order in which they should be executed to avoid circular dependencies.DFS does not directly provide dependency management; it is primarily used for the exploration and analysis of the graph's structure.
In summary, Topological Sort is a specific algorithm used to find a linear ordering of vertices in a Directed Acyclic Graph (DAG), while Depth-First Search is a more general graph traversal algorithm used to explore and analyze the structure of a graph. Topological Sort is applicable only to DAGs and has specific use cases like task scheduling, while DFS can be applied to various types of graphs for different purposes.