有的石头像莲花瓣,有的像大象头,有的像老人,有的像卧虎,有的错落成桥, 有的兀立如柱,有的侧身探海,有的怒目相向. Some bore no resemblance to anything known , but glowered black and motionless, blocking your way.
A vertex with zero outdegree is called a sink.出度为零的顶点称作收点.Vertex a is the initial vertex and b is the terminal vertext.a顶点是始端顶点,而b是末端顶点.An edge corresponds to a corridor and a vertex to the conjunction of several corrido...