Topological Sort of a Directed Acyclic Graph
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Overview
This is a very useful algorithm when a set of tasks that have precedence constraints between them need to be sequenced - executed in order. The topological sort can be done in a straightforward recursive way or using Depth-First Search (DFS).
Straightforward Algorithm
We use the observation that a DAG must have one or more sink vertices. The algorithm starts with a sink vertex, assigns to it the largest possible label, deletes the respective sink vertex from the graph, and repeats until there are no more vertices.
Straightforward_Topological_Sort(Graph G) let v be a sink vertex of G set f(v) = n Straightforward_Topological_Sort(G - {v})