View Code of Problem 3937

//----fishman@Willian
#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
const double esp = 1e-8;
int sgn(double x) {
    if (fabs(x) < esp)return 0;
    return x < 0 ? -1 : 1;
}
int dcmp(double x, double y) {
    if (sgn(x - y) == 0)return 0;
    return x < y ? -1 : 1;
}

struct Point {
    double x, y;
    Point() {}
    Point(double x, double y) :x(x),y(y) {}
    Point operator + (Point B) { return Point(x + B.x, y + B.y); }
    Point operator - (Point B) { return Point(x - B.x, y - B.y); }
    Point operator * (double k){return Point(x*k,y*k);}
    Point operator / (double k){return Point(x/k,y/k);}
    bool operator==(Point B) { return sgn(x - B.x) == 0 && sgn(y - B.y) == 0; }
    bool operator< (Point B) { return sgn(x - B.x) < 0 || (sgn(x - B.x) == 0 && sgn(y - B.y) < 0); }
    void input(){scanf("%lf%lf",&x,&y);}
};
typedef Point Vector;                                   //定义向量
double Dot(Vector A,Vector B){return A.x*B.x+A.y*B.y;}  //点积
double Len(Vector A){return sqrt(Dot(A,A));}             //向量的长度
double Len2(Vector A){return Dot(A,A);}                 //向量长度的平方
//A与B的夹角
double Angle(Vector A,Vector B){return acos(Dot(A,B)/Len(A)/Len(B));}
double Cross(Vector A,Vector B){return A.x*B.y-A.y*B.x;}
//三点面积
double Area2(Point A,Point B,Point C){return fabs(Cross(B-A,C-A));}
double Area(Point A,Point B,Point C){return 0.5*fabs(Cross(B-A,C-A));}
//距离
double Dis(Point A,Point B){return hypot(A.x-B.x,A.y-B.y);}

Point Cross_Point(Point a,Point b,Point c,Point d){//line ab cd
    double s1=Cross(b-a,c-a);
    double s2=Cross(b-a,d-a);
    return Point(c.x*s2-d.x*s1,c.y*s2-d.y*s1)/(s2-s1);
}
bool Cross_segement(Point a,Point b,Point c,Point d){//line ab,cd
    double s1=Cross(b-a,c-a),s2=Cross(b-a,d-a);
    double t1=Cross(d-c,a-c),t2=Cross(d-c,b-c);
    return sgn(s1)*sgn(s2)<=0&&sgn(t2)*sgn(t1)<=0;//1相交，0不相交
}
bool ins(Point x,Point a,Point b,Point c){//x是否在三角形abc内，1是，0否
   return !(Area(a,b,c)-Area(a,b,x)-Area(a,c,x)-Area(b,c,x));
}
int main()
{
    int t;
    cin>>t;
    while(t--){
        Point a1,b1,a2,b2;
        a1.input();b1.input();
        a2.input();b2.input();
        int flag=1;
        if(Cross_segement(a1,b1,a2,b2)==0){printf("0.00\n");continue;}
        Point o=Cross_Point(a1,b1,a2,b2);
        Point s,t;
        int cnt=0;
        if(a1.y>o.y){s=a1;++cnt;}
        if(b1.y>o.y){s=b1;++cnt;}
        if(a2.y>o.y){t=a2;++cnt;}
        if(b2.y>o.y){t=b2;++cnt;}

        if(cnt!=2){printf("0.00\n");continue;}
        if(ins(s,Point(t.x,o.y),o,t)==1||ins(t,Point(s.x,o.y),o,s)==1){printf("0.00\n");continue;}

        Point q,tmp;
        double ans=0;
        if(s.y<t.y){
            q=Cross_Point(s,Point(s.x+1,s.y),a2,b2);
            ans=Area(o,s,q);
        }
        else{
            q=Cross_Point(t,Point(t.x+1,t.y),a1,b1);
            ans=Area(o,t,q);
        }
        printf("%.2f\n",ans);

    }

    return 0;
}