POJ 1410 Intersection(判断线段是否在矩形面里)

题意：给你线段和矩形，问是否相交，或矩形包含线段；

注意：线段相交时，<(0,0),(1,0)> 和<(3,0),(4,0)> 不相交。。。。郁闷死了。。

#include <iostream>#include <cstdio>#include <cstring>#include <algorithm>#include <cmath>#include <queue>using namespace std;const double INF = 1e20;const double EPS = 1e-6;bool zero(double t){return -EPS<t&&t<EPS;}struct cvector{    double x,y;    cvector(double a,double b){x=a,y=b;}    cvector(){}};cvector operator+(cvector a,cvector b){    return cvector(a.x+b.x,a.y+b.y);}cvector operator-(cvector a,cvector b){    return cvector(b.x-a.x,b.y-a.y);}cvector operator*(double a,cvector b){    return cvector(a*b.x,a*b.y);}double operator*(cvector a,cvector b){    return a.x*b.x+a.y*b.y;}double operator^(cvector a,cvector b){    return a.x*b.y-b.x*a.y;}double length(double t){return t>0?t:-t;}double length(cvector t){return sqrt(t*t);}struct cpoint{    double x,y;    cpoint(double a,double b){x=a,y=b;}    cpoint(){}};cvector operator-(cpoint a,cpoint b){    return cvector(b.x-a.x,b.y-a.y);}double dist(cpoint a,cpoint b){    return length(b-a);}struct cline{    cpoint a,b;};bool intersect(cline a,cline b){    if(zero((a.a-a.b)^(b.a-b.b))) return false;    return ((a.a-b.a)^(b.b-b.a))*((a.b-b.a)^(b.b-b.a))<EPS&&    ((b.a-a.a)^(a.b-a.a))*((b.b-a.a)^(a.b-a.a))<EPS;}cpoint st,en;cline b[4],tmp;bool in(cpoint t){    for(int i=0;i<4;i++)    if(((t-b[i].a)^(b[i].b-b[i].a))>EPS)    {        return false;    }    return true;}int main(){    freopen("in.txt","r",stdin);    int cas;    scanf("%d",&cas);    while(cas--)    {        scanf("%lf%lf%lf%lf",&tmp.a.x,&tmp.a.y,&tmp.b.x,&tmp.b.y);        scanf("%lf%lf%lf%lf",&st.x,&st.y,&en.x,&en.y);        if(st.x>en.x) swap(st.x,en.x);        if(st.y<en.y) swap(st.y,en.y);        b[0].a.x=st.x,b[0].a.y=en.y;b[0].b=en;        b[1].a=en;b[1].b.x=en.x,b[1].b.y=st.y;        b[2].a=b[1].b;b[2].b=st;        b[3].a=st;b[3].b = b[0].a;        if(in(tmp.a)||in(tmp.b))        {            printf("T\n"); continue;        }        bool f =false;        for(int i=0;i<4;i++)        if(intersect(tmp,b[i]))        {            f = true;break;        }        if(f)        printf("T\n");        else        printf("F\n");    }    return 0;}