(From Wikipedia) The line graph L(G) of an undirected graph G is another graph L(G) that represents the adjacencies between edges of G. By definition, each vertex of L(G) represents an edge of G, and two vertices of L(G) are adjacent if and only if their corresponding edges share a common endpoint ("are adjacent") in G.
(维基百科)无向图G的线图L(G)的是另一种曲线图,L(G)表示的邻接边缘之间的G.根据定义,每个顶点的L(G)表示的G的边缘,和两个L(G)的顶点的相邻的,当且仅当它们的相应的边共享一个共同的端点(“邻接”)在G中