poj 1410 线段相交判断

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <iostream>
#include <algorithm>
#include <math.h>

using namespace std;
typedef struct point
{
    int x,y;
}point;

typedef struct line
{
    point st,ed;
}line;

int crossProduct(point a,point b,point c)
{
    return (c.x-a.x)*(b.y-a.y)-(c.y-a.y)*(b.x-a.x);
}

bool onSegment(point a,point b,point c)
{
    int maxx=max(a.x,b.x);
    int maxy=max(a.y,b.y);
    int minx=min(a.x,b.x);
    int miny=min(a.y,b.y);
    if(crossProduct(a,b,c)==0&&(c.x<=maxx)&&(c.x>=minx)&&(c.y<=maxy)&&(c.y>=miny))
    {
        return true;
    }
    return false;
}

bool segIntersect(point p1,point p2,point p3,point p4)
{
    int d1=crossProduct(p3,p4,p1);
    int d2=crossProduct(p3,p4,p2);
    int d3=crossProduct(p1,p2,p3);
    int d4=crossProduct(p1,p2,p4);
    if(d1*d2<0 && d3*d4<0)
        return true;
    if(d1==0 && onSegment(p3,p4,p1))
        return true;
    if(d2==0 && onSegment(p3,p4,p2))
        return true;
    if(d3==0 && onSegment(p1,p2,p3))
        return true;
    if(d4==0 && onSegment(p1,p2,p4))
        return true;
    return false;
}

point p[5];
line li[5];
int num[1005];

int main()
{
    int n,m,i,j;
    line tmp;
    int xleft,ytop,xright,ybottom;
    scanf("%d",&n);
    while(n--)
    {
        scanf("%d%d%d%d%d%d%d%d",&tmp.st.x,&tmp.st.y,&tmp.ed.x,&tmp.ed.y
              ,&xleft,&ytop,&xright,&ybottom);
        li[0].st.x=xleft;
        li[0].st.y=ytop;
        li[0].ed.x=xleft;
        li[0].ed.y=ybottom;

        li[1].st.x=xleft;
        li[1].st.y=ybottom;
        li[1].ed.x=xright;
        li[1].ed.y=ybottom;

        li[2].st.x=xright;
        li[2].st.y=ybottom;
        li[2].ed.x=xright;
        li[2].ed.y=ytop;

        li[3].st.x=xright;
        li[3].st.y=ytop;
        li[3].ed.x=xleft;
        li[3].ed.y=ytop;

        bool flag=true;
        for(i=0;i<4;i++)
        {
            if(segIntersect(tmp.st,tmp.ed,li[i].st,li[i].ed))
            {
                flag=false;
                break;
            }
        }

        int maxx=max(xleft,xright);
        int maxy=max(ytop,ybottom);
        int minx=min(xleft,xright);
        int miny=min(ytop,ybottom);
        if(tmp.st.x<=maxx&&tmp.st.x>=minx&&tmp.st.y>=miny&&tmp.st.y<=maxy
           ||tmp.ed.x<=maxx&&tmp.ed.x>=minx&&tmp.ed.y>=miny&&tmp.ed.y<=maxy)
            flag=false;

        if(flag)
            printf("F\n");
        else printf("T\n");
    }
    return 0;
}