A1397 | [COCI-2020-2021-contest6]#4 Geometrija
来源COCI
时间限制1s
内存限制128MB
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题目描述
You are given n points on the plane, such that no three points lie on the same line.
We say that line segments AB and CD cross if they share a point X different from the points A, B, C and D.
Let S be the set of all line segments between pairs of the given points. Find the number of segments in S that don’t cross with any other segment in S.
We say that line segments AB and CD cross if they share a point X different from the points A, B, C and D.
Let S be the set of all line segments between pairs of the given points. Find the number of segments in S that don’t cross with any other segment in S.
输入格式
The first line contains an integer n (3 ≤ n ≤ 1000), the number of points.
The following n lines contain integers xi and yi (−10^9 ≤ xi, yi ≤ 10^9), the coordinates of the points.
The following n lines contain integers xi and yi (−10^9 ≤ xi, yi ≤ 10^9), the coordinates of the points.
输出格式
Output the requested number of segments.
输入输出样例
输入 #1
4 1 1 -1 1 -1 -1 1 -1
输出 #1
4
Output the requested number of segments.
C++ 编辑器
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评测结果：Accepted