POJ1410_还是没考虑全面——线段是否与矩形有共同的垂直投影

题意如题目

有几个点1.怪我没读好题目：给出的矩形两个端点不一定都是左上右下，但是肯定能勾勒出一个矩形。

2.现在才发现很多线段相交的判断我都没有仔细考虑这一个问题

bool ssinsert(Point p1,Point p2,Point p3,Point p4)
{

    if(p1.x == p2.x && p3.x == p4.x && p2.x == p3.x)
    {
        if(max(p1.y,p2.y) < min(p3.y,p4.y) || min(p1.y,p2.y) > max(p3.y,p4.y))return false;
        else return true;
    }
    if(p1.y == p2.y && p3.y == p4.y && p2.y == p3.y)
    {
        if(max(p1.x,p2.x) < min(p3.x,p4.x) || min(p1.x,p2.x) > max(p3.x,p4.x))return false;
        else return true;
    }
    if(cross(p1,p2,p3) * cross(p1,p2,p4) < eps &&
       cross(p3,p4,p1) * cross(p3,p4,p2) < eps)return true;
    return false;
}

 对于很多不需要严格线段相交的题目，也就是有一条线段的端点在另一条线段上，这样结果就是零，但是这样判断的共线是共直线如果两个线段的判定都平行于x轴但没有焦点，就会误判，所以前面我做了预处理

#include <iostream>
#include <vector>
#define eps 1e-10
using namespace std;
struct Point
{
    double x,y;
    Point (double x = 0.0,double y = 0.0):x(x),y(y){}
    Point operator - (Point p){return Point(x - p.x,y - p.y);}
};
struct segment
{
    Point p1,p2;
    segment(Point p1 = Point(0.0,0.0),Point p2 = Point(0.0,0.0)):p1(p1),p2(p2){}
};
vector<segment> ls;
void init()
{
    ls.clear();
}
double cross(Point p0,Point p1,Point p2)
{
    Point a = p1 - p0;
    Point b = p2 - p0;
    return a.x * b.y - a.y * b.x;
}
bool ssinsert(Point p1,Point p2,Point p3,Point p4)
{

    if(p1.x == p2.x && p3.x == p4.x && p2.x == p3.x)
    {
        if(max(p1.y,p2.y) < min(p3.y,p4.y) || min(p1.y,p2.y) > max(p3.y,p4.y))return false;
        else return true;
    }
    if(p1.y == p2.y && p3.y == p4.y && p2.y == p3.y)
    {
        if(max(p1.x,p2.x) < min(p3.x,p4.x) || min(p1.x,p2.x) > max(p3.x,p4.x))return false;
        else return true;
    }
    if(cross(p1,p2,p3) * cross(p1,p2,p4) < eps &&
       cross(p3,p4,p1) * cross(p3,p4,p2) < eps)return true;
    return false;
}
bool inner(Point p1,Point p2,Point p3,Point p4)
{
    if(min(p1.y,p2.y) >= min(p3.y,p4.y) && max(p1.y,p2.y) <= max(p3.y,p4.y) &&
       min(p1.x,p2.x) >= min(p3.x,p4.x) && max(p1.x,p2.x) <= max(p3.x,p4.x))return true;
    return false;
}
int main()
{
    int t;
    double x1,y1,x2,y2;
    scanf("%d",&t);
    while(t--)
    {
        ls.clear();
        scanf("%lf%lf%lf%lf",&x1,&y1,&x2,&y2);
        ls.push_back(segment(Point(x1,y1),Point(x2,y2)));
        scanf("%lf%lf%lf%lf",&x1,&y1,&x2,&y2);
        double minx = min(x1,x2);
        double maxx = max(x1,x2);
        double miny = min(y1,y2);
        double maxy = max(y1,y2);
        Point a(minx,miny);         Point b(minx,maxy);
        Point c(maxx,maxy);         Point d(maxx,miny);
        //printf("a  %lf %lf
 b %lf %lf
c %lf %lf
d %lf %lf
",a.x,a.y,b.x,b.y,c.x,c.y,d.x,d.y);
        ls.push_back(segment(a,b));      ls.push_back(segment(b,c));
        ls.push_back(segment(c,d));      ls.push_back(segment(d,a));
        int flag = 0;
        for(int i = 1;i < ls.size();i++)
        {
            if(ssinsert(ls[0].p1,ls[0].p2,ls[i].p1,ls[i].p2) || inner(ls[0].p1,ls[0].p2,b,d))
            {
                flag = 1;
                break;
            }
        }
        if(flag)
        {
            printf("T
");
        }
        else
        {
            printf("F
");
        }

    }
    return 0;
}