A12519 | $Satanic Panic$

时间限制1s

内存限制256MB

通过 / 提交0/0

题目描述

You are given a set of $n$ points in a 2D plane. No three points are collinear. A pentagram is a set of $5$ points $A,B,C,D,E$ that can be arranged as follows. ![](/uploads/acgo/image/bf317dad30978a28_05708a4e91fb.jpeg) Note the length of the line segments don't matter, only that those particular intersections exist. Count the number of ways to choose $5$ points from the given set that form a pentagram.

The first line contains an integer $n$ ( $5 \leq n \leq 300$ ) — the number of points. Each of the next $n$ lines contains two integers $x_i, y_i$ ( $-10^6 \leq x_i,y_i \leq 10^6$ ) — the coordinates of the $i$ -th point. It is guaranteed that no three points are collinear.

Print a single integer, the number of sets of $5$ points that form a pentagram.

输入 #1

输出 #1

输入 #2

输出 #2

输入 #3

10
841746 527518
595261 331297
-946901 129987
670374 -140388
-684770 309555
-302589 415564
-387435 613331
-624940 -95922
945847 -199224
24636 -565799

输出 #3

C++ 编辑器

输入

输出