hdu1071（抛物线，直线以及二重积分）

http://acm.hdu.edu.cn/showproblem.php?pid=1071

//抛物线 yp=a*(x-b)^2+c;
//直线 yz=k*x+s;
//二重积分公式： f(x0,x1)(yp-yz)*dx;

#include"iostream"
usingnamespace std;
double a,b,c,k,s;
double fun(double x)
{
    return1.0*(a*x*x*x/3)-1.0*(a*b+k/2)*x*x+(a*b*b+c-s)*x;
}
int main()
{
    int t;
    double x1,y1,x2,y2,x3,y3;
    scanf("%d",&t);
    while(t--)
    {
        scanf("%lf%lf%lf%lf%lf%lf",&x1,&y1,&x2,&y2,&x3,&y3);
       
        k=(y3-y2)/(x3-x2);
        s=y3-k*x3;

        a=(y2-y1)/((x2-x1)*(x2-x1));
        b=x1;
        c=y1;

        double area=1.0*(fun(x3)-fun(x2));
          printf("%.2lf\n",area);
    }
    return0; 
}