Directed acyclic graphs (DAG)

An acyclic graph is a graph without a cycle or loop. If we want to visit other nodes from a particular node, we will not visit any of the nodes twice. A directed acyclic graph, popularly known as a DAG, is a directed graph that is acyclic. A directed acyclic graph has many usages in graph algorithms. A directed acyclic graph has a topological ordering, where the ordering of the vertices is such that the starting endpoint of every edge occurs earlier in the ordering than the ending endpoints of the edges. The following diagram represents a DAG:

From the first look, it seems that B, C, E, and D form a cycle, but ...

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