hdu1071(抛物线,直线以及二重积分)
http://acm.hdu.edu.cn/showproblem.php?pid=1071
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
//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;
}
//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;
}