hdu1071The area(计算几何)

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题目链接

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

The area

Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 8691 Accepted Submission(s): 6091

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

25.000000 5.0000000.000000 0.00000010.000000 0.00000010.000000 10.0000001.000000 1.00000014.000000 8.222222

简单的计算几何，这道题全是是高中的知识。。好像没有什么好说的。。就是不要被图干扰了，图上画得像是二次函数，其实是抛物线=，=

AC代码

#include<stdio.h>#include<math.h>int main(){    double a,b,d,x1,x2,x3,y1,y2,y3,k;    double a1,a2,a3,a4,a0;    int T;    double q;    scanf("%d",&T);    while(T--){        q=0;        scanf("%lf%lf%lf%lf%lf%lf",&x1,&y1,&x2,&y2,&x3,&y3);        k=(y3-y2)/(x3-x2);        d=y3-k*x3;        a=(y2-y1)/((x2-x1)*(x2-x1));        a2=a,a1=-2*a*x1-k,a0=a*x1*x1+y1-d;        q=a2*x3*x3*x3/3+a1*x3*x3/2+a0*x3-(a2*x2*x2*x2/3+a1*x2*x2/2+a0*x2);        printf("%.2lf\n",q);    }}

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