Figure 2.

Maximum matching in directed networks. (a) Simple, unweighted directed graph with four nodes and four edges. (b) Result of maximum matching in the directed network. Edge a ₂₁ cannot be a member of the disjoint set of edges, as it has a common starting point with a ₃₁ and a common end point with a ₂₃. End points of matched edges are matched nodes. (c) Undirected representation of the directed network. For each node in the directed network there are two nodes in the undirected representation, one for outgoing edges and one for incoming edges. The representation of edges is obvious. The result of maximum matching is the same in both directed and undirected representations.