HDU 1071 The area

题解：求抛物线系数公式，直线系数公式，再用简单积分来求面积。

#include <cstdio>  
double x1,x2,x3,y1,y2,y3;  
double a,s,k;  
double fuck(double x)  
{  
    return 1.0/3*a*(x-x1)*(x-x1)*(x-x1)+y1*x-1.0/2*k*(x-x3)*(x-x3)-y3*x;  
}  
int main()  
{  
    int t;  
    scanf("%d",&t);  
    while(t--)  
    {  
        scanf("%lf%lf%lf%lf%lf%lf",&x1,&y1,&x2,&y2,&x3,&y3);  
        k=(y2-y3)/(x2-x3);  
        a=(y2-y1)/((x2-x1)*(x2-x1));  
        s=fuck(x3)-fuck(x2);  
        printf("%.2lf\n",s);  
    }  
    return 0;  
}