Definitions A cycle in a directed graph is a path of length at least 1 such that wi=w;this cycle is simple if the path is simple. For undirected graphs,we require that the edges be distinct;that is,the path u,v,win an undirected graph should not be considered a cycle,because (u, v and (v,u)are the same edge.In a directed graph, these are different edges,so it makes sense to call this a cycle. A directed graph is acyclic if it has no cycles.Definitions ◼ A cycle in a directed graph is a path of length at least 1 such that w1=wn ; this cycle is simple if the path is simple. ◼ For undirected graphs, we require that the edges be distinct; that is, the path u, v, u in an undirected graph should not be considered a cycle, because (u, v) and (v, u) are the same edge. In a directed graph, these are different edges, so it makes sense to call this a cycle. ◼ A directed graph is acyclic if it has no cycles