UVA_11343_Isolated Segments_WA

#include<iostream>
#include<sstream>
#include<string>
#include<vector>
#include<list>
#include<set>
#include<map>
#include<stack>
#include<queue>
#include<algorithm>
#include<numeric>
#include<cmath>
#pragma warning(disable:4996)
using std::cin;
using std::cout;
using std::endl;
using std::stringstream;
using std::string;
using std::vector;
using std::list;
using std::pair;
using std::set;
using std::multiset;
using std::map;
using std::multimap;
using std::stack;
using std::queue;
using std::priority_queue;
class Point
{
public:
	long double x, y;
	Point() {}
	Point(const long double &X, const long double &Y)
	{
		x = X;
		y = Y;
	}
};
class Line
{
public:
	long double a, b, c;//ax+by=c
	long double x_min, x_max, y_min, y_max;//直线的值域
	Line() {}
	Line(const Point &first, const Point &second)
	{
		x_min = std::min(first.x, second.x);
		x_max = std::max(first.x, second.x);
		y_min = std::min(first.y, second.y);
		y_max = std::max(first.y, second.y);
		if (first.x != second.x)//斜率式可行
		{
			b = 1;
			a = -(first.y - second.y) / (first.x - second.x);
			c = first.y + a*first.x;
		}
		else//k->无穷
		{
			b = 0;
			a = 1;
			c = first.x;
		}
	}
	bool lineIntersected(const Line &line)//直线相交的判定
	{
		auto D = a*line.b - line.a*b;
		if (D)
		{
			return true;
		}
		return false;
	}
	bool lineParallel(const Line&line)//判断两直线是否平行
	{
		auto D = a*line.b - line.a*b;
		if (!D)
		{
			return true;
		}
		return false;
	}
	bool lineOverlapped(const Line&line)//判断两直线是否重合（平行的特例）
	{
		auto D = a*line.b - line.a*b;
		auto Dx = c*line.b - line.c*b;
		auto Dy = a*line.c - line.a*c;
		if (!D&&!Dx&&!Dy)
		{
			return true;
		}
		return false;
	}
	long double fixed(long double value)
	{
		value *= 1000000000000.0;
		value += 0.5;
		value = floor(value);
		value /= 1000000000000.0;
		return value;
	}
	Point getIntersection(const Line&line)//行列式求两直线交点,要修正误差
	{
		auto D = a*line.b - line.a*b;
		auto Dx = c*line.b - line.c*b;
		auto Dy = a*line.c - line.a*c;
		return{ fixed(Dx / D),fixed(Dy / D) };
	}
	bool segmentIntersected(const Line &line)
	{
		if (lineIntersected(line))
		{
			auto point = getIntersection(line);
			if (point.x >= x_min&&point.x <= x_max
				&&point.y >= y_min&&point.y <= y_max
				&&point.x >= line.x_min&&point.x <= line.x_max
				&&point.y >= line.y_min&&point.y <= line.y_max
				)//交点在两线段的值域内
			{
				return true;
			}
		}
		return false;
	}
	bool segmentOverlapped(const Line &line)
	{
		if (lineOverlapped(line))
		{
			if ((x_min <= line.x_max&&x_min >= line.x_min) || (x_max <= line.x_max&&x_max >= line.x_min))
			{
				return true;
			}
		}
		return false;
	}
};
class Rectangle
{
public:
	int left, right, top, bottom;
	bool inRectangle(const Point &point)
	{
		if (point.x >= left&&point.x <= right&&point.y >= bottom&&point.y <= top)
		{
			return true;
		}
		return false;
	}
};
int main()
{
	//freopen("input.txt", "r", stdin);
	//freopen("output.txt", "w", stdout);
	int T;
	while (cin >> T)
	{
		while (T--)
		{
			int n; cin >> n;
			vector<Line>line;
			for (int i = 0; i < n; i++)
			{
				long double x1, x2, y1, y2;
				cin >> x1 >> y1 >> x2 >> y2;
				line.push_back({ { x1,y1 },{ x2,y2 } });
			}
			vector<bool>collided(n);
			for (int i = 0; i<n; i++)
			{
				for (int j = i + 1; j < n; j++)
				{
					if (line[i].segmentIntersected(line[j]) || line[i].segmentOverlapped(line[j]))
					{
						collided[i] = collided[j] = true;
					}
				}
			}
			cout << std::count(collided.begin(), collided.end(), false) << endl;
		}
	}
	return 0;
}