HDU 6354 Everything Has Changed 圆相交模板水题

最新推荐文章于 2019-07-25 20:18:00 发布

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最新推荐文章于 2019-07-25 20:18:00 发布 · 369 阅读

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本文介绍了一种计算在多个圆形切割区域作用下大圆剩余部分外周长的方法。通过判断小圆与大圆的位置关系，并计算相应的圆心角来得出最终答案。

Problem Description

Edward is a worker for Aluminum Cyclic Machinery. His work is operating mechanical arms to cut out designed models. Here is a brief introduction of his work.
Assume the operating plane as a two-dimensional coordinate system. At first, there is a disc with center coordinates (0,0) and radius R. Then, m mechanical arms will cut and erase everything within its area of influence simultaneously, the i-th area of which is a circle with center coordinates (xi,yi) and radius ri (i=1,2,⋯,m). In order to obtain considerable models, it is guaranteed that every two cutting areas have no intersection and no cutting area contains the whole disc.
Your task is to determine the perimeter of the remaining area of the disc excluding internal perimeter.
Here is an illustration of the sample, in which the red curve is counted but the green curve is not.