Grid method is an improved algorithm of the directed-loop method: it utilizes the orientation of the polygon and region partition at the same time.

网格法是有向回路法的改进算法，利用了多边形的方向性和区域划分。

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An algorithm for identifying the orientation of a polygon according to the sequence of extremity vertexes is proposed.

提出一种根据多边形各个极点在顶点序列中的先后顺序确定多边形方向的算法。

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Meanwhile, the sufficient and necessary condition for the orientation of an arbitrary simple polygon is given.

同时，给出了任意简单多边形走向的充要条件。

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