附上生成数据的代码：
```cpp
#include<cstdio>
#include<ctime>
#include<cstdlib>
#include<algorithm>
#include<cstdio>
int main(){
srand(time(NULL));
int n=rand()%16;
printf("%d\n",n);
double a,b;
for(int i=0;i<n;i++)
{
a=rand()%10000+1;a/=100;if(rand()%2)a=-a;
b=rand()%10000+1;b/=100;if(rand()%2)b=-b;
printf("%.2lf %.2lf\n",a,b);
}
return 0;
}
```
by Robert @ 2017-11-02 11:09:16
这题水到爆炸。。
我错把x1 x2 y1 y2弄了个int类型的，居然还能过9组数据，，
by Ch4rc0al @ 2018-04-10 14:16:09