Description
There is a number of disjoint vertical line segments in the plane. We say that two segments are horizontally visible if they can be connected by a horizontal line segment that does not have any common points with other vertical segments. Three different vertical segments are said to form a triangle of segments if each two of them are horizontally visible. How many triangles can be found in a given set of vertical segments?
Task
Write a program which for each data set:
reads the description of a set of vertical segments,
computes the number of triangles in this set,
writes the result.
Input
The first line of the input contains exactly one positive integer d equal to the number of data sets, 1 <= d <= 20. The data sets follow.
The first line of each data set contains exactly one integer n, 1 <= n <= 8 000, equal to the number of vertical line segments.
Each of the following n lines consists of exactly 3 nonnegative integers separated by single spaces:
yi', yi'', xi - y-coordinate of the beginning of a segment, y-coordinate of its end and its x-coordinate, respectively. The coordinates satisfy 0 <= yi' < yi'' <= 8 000, 0 <= xi <= 8 000. The segments are disjoint.
Output
The output should consist of exactly d lines, one line for each data set. Line i should contain exactly one integer equal to the number of triangles in the i-th data set.
Sample Input
1
5
0 4 4
0 3 1
3 4 2
0 2 2
0 2 3
Sample Output
1
题意是如果两条线段之间能被一条平行于x轴的线段相连且这条线段和其他线段没有交点，那么这两条线段可见，如果三条线段每两条线段可见，那么他们能组成特定三角形，那么问三角形有多少个。这题先把所有线段储存起来，按x大小升序排列，然后相当于依次读入不同颜色的线段，每次操作，先判断这条线段所在的纵坐标范围内颜色种类，这些颜色种类对应的线段和当前这条线段是可见的，接着把这条线段插入区间，更新总区间的颜色。这里有一点要注意，为了避免单位元线段被“忽略”，把所有的纵坐标都乘2.如3 0 4 1 0 2 2 3 4 2这组数据不乘2的话2-3会被忽略。刚开始所有颜色都为0，如果线段是纯色，那么为大于0的数，若为-1，则是杂色，要在子区间找。
?
?
#include
#include
#include
#include
#include
#include
?
?
?