A12519. Satanic Panic
编程题
普及/提高-
知识点
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.  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.
A pentagram is a set of $5$ points $A,B,C,D,E$ that can be arranged as follows.  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.
输入格式
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.
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.
输出格式
Print a single integer, the number of sets of $5$ points that form a pentagram.
输入输出样例
输入 #1
5 0 0 0 2 2 0 2 2 1 3
输出 #1
1
输入 #2
5 0 0 4 0 0 4 4 4 2 3
输出 #2
0
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
85
说明/提示
A picture of the first sample:  A picture of the second sample:  A picture of the third sample: 