hdoj 1071 The area

The area

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 8388    Accepted Submission(s):
5888

Problem Description

Ignatius bought a land last week, but he didn't know
the area of the land because the land is enclosed by a parabola and a straight
line. The picture below shows the area. Now given all the intersectant points
shows in the picture, can you tell Ignatius the area of the land?

Note:
The point P1 in the picture is the vertex of the parabola.

 

Input

The input contains several test cases. The first line
of the input is a single integer T which is the number of test cases. T test
cases follow.
Each test case contains three intersectant points which shows
in the picture, they are given in the order of P1, P2, P3. Each point is
described by two floating-point numbers X and
Y(0.0<=X,Y<=1000.0).

 

Output

For each test case, you should output the area of the
land, the result should be rounded to 2 decimal places.

 

Sample Input

2

5.000000 5.000000

0.000000 0.000000

10.000000 0.000000

10.000000 10.000000

1.000000 1.000000

14.000000 8.222222

 

Sample Output

33.33

40.69

 

就是一道数学题，做题的时候看错了一个坐标  结果看了好长时间没发现  坑~~~~

#include<stdio.h>
#include<math.h>
int main()
{
	int N;
	double a,b,c,d,k,x1,y1,x2,y2,x3,y3,s;
	scanf("%d",&N);
	while(N--)
	{
		s=0;
		scanf("%lf%lf%lf%lf%lf%lf",&x1,&y1,&x2,&y2,&x3,&y3);
		a=((y1-y3)*(x1-x2)-(y1-y2)*(x1-x3))/((x1*x1-x3*x3)*(x1-x2)-(x1*x1-x2*x2)*(x1-x3));
		d=((y1-y3)-a*(x1*x1-x3*x3))/(x1-x3);
		c=y1-a*x1*x1-d*x1;
		k=(y2-y3)/(x2-x3);
		b=y3-k*x3;
		s=((a*x3*x3*x3)/3+((d-k)*x3*x3)/2+(c-b)*x3)-((a*x2*x2*x2)/3+((d-k)*x2*x2)/2+(c-b)*x2);
		printf("%.2lf\n",s);
	}
	return 0;
}