What is the topological sorting algorithm in graph theory?

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What is the topological sorting algorithm in graph theory?

The topological sorting algorithm in graph theory is known as the "Topological Sort" or "Topological Sorting". It is used to linearly order the vertices of a directed acyclic graph (DAG) in such a way that for every directed edge (u, v), vertex u comes before vertex v in the ordering. In other words, it arranges the vertices in a way that respects the partial order defined by the directed edges.

The most commonly used algorithm for topological sorting is the "Depth-First Search" (DFS) algorithm. The algorithm starts by selecting a random vertex and performs a depth-first search traversal on the graph. During the traversal, it marks the visited vertices and recursively explores the unvisited neighbors of each vertex. Once a vertex has no unvisited neighbors, it is added to the front of the topological ordering.

The algorithm continues this process until all vertices have been visited. The resulting ordering represents a valid topological sorting of the graph. If the graph contains a cycle, the algorithm will not be able to complete the sorting, as a cycle violates the acyclic property required for topological sorting.

The time complexity of the topological sorting algorithm using DFS is O(V + E), where V is the number of vertices and E is the number of edges in the graph. This algorithm is widely used in various applications, such as task scheduling, dependency resolution, and determining the order of events in a system.