POJ 1418 圆的基本操作以及圆弧离散化

最新推荐文章于 2024-10-20 10:24:08 发布

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最新推荐文章于 2024-10-20 10:24:08 发布

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分类专栏：计算几何

本文链接：https://blog.youkuaiyun.com/xianxingwuguan1/article/details/37565971

该博客详细解析了POJ 1418编程题，主要探讨如何处理圆的基本操作，并介绍在解决过程中进行圆弧离散化的策略。内容包括输入输出格式说明、样例输入输出分析，以及针对可见圆计数问题的思路讨论。

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Viva Confetti

Time Limit: 1000MS		Memory Limit: 10000K
Total Submissions: 761		Accepted: 319

Description

Do you know confetti? They are small discs of colored paper, and people throw them around during parties or festivals. Since people throw lots of confetti, they may end up stacked one on another, so there may be hidden ones underneath.

A handful of various sized confetti have been dropped on a table. Given their positions and sizes, can you tell us how many of them you can see?

The following figure represents the disc configuration for the first sample input, where the bottom disc is still visible.

Input

The input is composed of a number of configurations of the following form.

n
x1 y1 r1
x2 y2 r2
...
xn yn rn

The first line in a configuration is the number of discs in the configuration (a positive integer not more than 100), followed by one line descriptions of each disc : coordinates of its center and radius, expressed as real numbers in decimal notation, with up to 12 digits after the decimal point. The imprecision margin is +/- 5 x 10^(-13). That is, it is guaranteed that variations of less than +/- 5 x 10^(-13) on input values do not change which discs are visible. Coordinates of all points contained in discs are between -10 and 10.

Confetti are listed in their stacking order, x1 y1 r1 being the bottom one and xn yn rn the top one. You are observing from the top.

The end of the input is marked by a zero on a single line.

Output

For each configuration you should output the number of visible confetti on a single line.

Sample Input

3
0 0 0.5
-0.9 0 1.00000000001
0.9 0 1.00000000001
5
0 1 0.5
1 1 1.00000000001
0 2 1.00000000001
-1 1 1.00000000001
0 -0.00001 1.00000000001
5
0 1 0.5
1 1 1.00000000001
0 2