POJ 1410 Intersection （线段和矩形相交）

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <string>
#include <cstring>
#include <algorithm>

using namespace std;
typedef long long ll;
typedef unsigned long long ull;
const int inf=0x3f3f3f3f;
const double eps=1e-10;
int n;
double x,y,xx,yy,tx,ty,txx,tyy;

int dcmp(double x){
    if(fabs(x)<eps) return 0;
    if(x<0) return -1;
    else return 1;
}

struct Point{
    double x,y;
    Point(){}
    Point(double _x,double _y){
        x=_x,y=_y;
    }
    Point operator + (const Point &b) const{
        return Point(x+b.x,y+b.y);
    }
    Point operator - (const Point &b) const{
        return Point(x-b.x,y-b.y);
    }
    double operator * (const Point &b) const{
        return x*b.x+y*b.y;
    }
    double operator ^ (const Point &b) const{
        return x*b.y-y*b.x;
    }
};

struct Line{
    Point s,e;
    Line(){}
    Line(Point _s,Point _e){
        s=_s,e=_e;
    }
};

bool inter(Line l1,Line l2){
    return 
        max(l1.s.x,l1.e.x)>=min(l2.s.x,l2.e.x) &&
        max(l2.s.x,l2.e.x)>=min(l1.s.x,l1.e.x) &&
        max(l1.s.y,l1.e.y)>=min(l2.s.y,l2.e.y) &&
        max(l2.s.y,l2.e.y)>=min(l1.s.y,l1.e.y) &&
        dcmp((l2.s-l1.e)^(l1.s-l1.e))*dcmp((l2.e-l1.e)^(l1.s-l1.e))<=0 &&
        dcmp((l1.s-l2.e)^(l2.s-l2.e))*dcmp((l1.e-l2.e)^(l2.s-l2.e))<=0;
}

int main(){
    scanf("%d",&n);
    while(n--){
        scanf("%lf%lf%lf%lf%lf%lf%lf%lf",&x,&y,&xx,&yy,&tx,&ty,&txx,&tyy);
        double xl=min(tx,txx);
        double xr=max(tx,txx);
        double ydown=min(ty,tyy);
        double yup=max(ty,tyy);
        Line line=Line(Point(x,y),Point(xx,yy));
        Line line1=Line(Point(tx,ty),Point(tx,tyy));
        Line line2=Line(Point(tx,ty),Point(txx,ty));
        Line line3=Line(Point(txx,ty),Point(txx,tyy));
        Line line4=Line(Point(txx,tyy),Point(tx,tyy));
        if(inter(line,line1) || inter(line,line2) || inter(line,line3) || inter(line,line4) || (max(x,xx)<xr && max(y,yy)<yup && min(x,xx)>xl && min(y,yy)>ydown)) printf("T\n");
        else printf("F\n");
    }
    return 0;
}