1 #include <iostream>  2 #include<cstdio>  3 #include<cstring>  4 #include<algorithm>  5 #include<stdlib.h>  6 #include<vector>  7 #include<cmath>  8 #include<queue>  9 #include<set> 10 using namespace std; 11 #define N 100000 12 #define LL long long 13 #define INF 0xfffffff 14 const double eps = 1e-8; 15 const double pi = acos(-1.0); 16 const double inf = ~0u>>2; 17 struct point 18 { 19     double x,y; 20     point(double x=0,double y=0):x(x),y(y) {} 21 } p[10]; 22 typedef point pointt; 23 pointt operator -(point a,point b) 24 { 25     return pointt(a.x-b.x,a.y-b.y); 26 } 27 int dcmp(double x) 28 { 29     if(fabs(x)<eps) return 0; 30     return x<0?-1:1; 31 } 32 double cross(point a,point b) 33 { 34     return a.x*b.y-a.y*b.x; 35 } 36 bool cmp(point a,point b) 37 { 38     return a.y>b.y; 39 } 40  41 bool intersection1(point p1, point p2, point p3, point p4, point& p)      // 直线相交 42 { 43     double a1, b1, c1, a2, b2, c2, d; 44     a1 = p1.y - p2.y; 45     b1 = p2.x - p1.x; 46     c1 = p1.x*p2.y - p2.x*p1.y; 47     a2 = p3.y - p4.y; 48     b2 = p4.x - p3.x; 49     c2 = p3.x*p4.y - p4.x*p3.y; 50     d = a1*b2 - a2*b1; 51     if (!dcmp(d))    return false; 52     p.x = (-c1*b2 + c2*b1) / d; 53     p.y = (-a1*c2 + a2*c1) / d; 54     return true; 55 } 56 double solve(point p1,point p2,point p3,point p4,point pp,point tp) 57 { 58     double ans; 59     point p11 = point(p1.x,p1.y+1); 60     if(dcmp(cross(p11-p1,p1-p3))==0) 61     { 62         ans = 0; 63         //cout<<","; 64     } 65     else 66     { 67         if(dcmp(cross(p11-p1,p1-p3))*dcmp(cross(p1-p2,p3-p4))<0) 68         { 69             ans = fabs(cross(p3-pp,tp-pp))/2; 70             //cout<<","; 71         } 72         else ans = 0; 73     } 74     return ans; 75 } 76 int on_segment( point p1,point p2 ,point p ) 77 { 78     double max=p1.x > p2.x ? p1.x : p2.x ; 79     double min =p1.x < p2.x ? p1.x : p2.x ; 80     double max1=p1.y > p2.y ? p1.y : p2.y ; 81     double min1=p1.y < p2.y ? p1.y : p2.y ; 82     if( p.x >=min && p.x <=max && 83             p.y >=min1 && p.y <=max1 ) 84         return 1; 85     else 86         return 0; 87 } 88 int main() 89 { 90     int t,i; 91     cin>>t; 92     while(t--) 93     { 94         for(i = 1; i <= 4 ; i++) 95             scanf("%lf%lf",&p[i].x,&p[i].y); 96         sort(p+1,p+3,cmp); 97         sort(p+3,p+5,cmp); 98         point pp; 99         if(intersection1(p[1],p[2],p[3],p[4],pp))100         {101             if(!on_segment(p[1],p[2],pp)||!on_segment(p[3],p[4],pp))102             {103                 puts("0.00");104                 continue;105             }106         }107         //cout<<pp.x<<" "<<pp.y<<endl;108         double ans;109         point p1 = point(p[3].x-1,p[3].y),p2;110         point p3 = point(p[1].x-1,p[1].y);111         if(intersection1(p[1],p[2],p[3],p1,p2)&&on_segment(p[1],p[2],p2))112         {113 114             ans = solve(p[1],p[2],p[3],p[4],pp,p2);115         }116         else117         {118             intersection1(p[3],p[4],p[1],p3,p2);119            // cout<<p2.x<<" "<<p2.y<<endl;120             ans = solve(p[3],p[4],p[1],p[2],pp,p2);121         }122         printf("%.2f\n",ans+eps);123 124     }125     return 0;126 }