对给定的Arc.gen文件采用左转算法构建拓扑关系，包括结点与弧段、弧段与结点、弧段与多边形、多边形与弧段的关系，并生成相应的文件-For a given algorithm Arc.gen documents to be left to build topology, including nodes and arcs, arcs and nodes, arcs and polygons, polygons with the relationship between the arcs and g