A1110. [COCI-2007_2008-contest2]#4 PRAVOKUTNI
编程题
普及+/提高
知识点
题目描述
N points are placed in the coordinate plane.
Write a program which calculates in how many ways a right triangle can be formed by three of the given points. A right triangle is one in which one of the angles is 90 degrees.
Write a program which calculates in how many ways a right triangle can be formed by three of the given points. A right triangle is one in which one of the angles is 90 degrees.
输入格式
The first line of input contains an integer N (3 ≤ N ≤ 1500), the number of points.
Each of the following N lines contains the coordinates of one point, two integers separated by a space.
The coordinates will be between −109 and 10
9.
No two points will be located at the same coordinates.
Each of the following N lines contains the coordinates of one point, two integers separated by a space.
The coordinates will be between −109 and 10
9.
No two points will be located at the same coordinates.
输出格式
Output the number of right triangles.
输入输出样例
输入 #1
3 4 2 2 1 1 3
输出 #1
1
输入 #2
4 5 0 2 6 8 6 5 7
输出 #2
0
输入 #3
5 -1 1 -1 0 0 0 1 0 1 1
输出 #3
7