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;  

}