NYOJ 67 三角形面积

 1 //三角形面积用到海伦公式：p=(a+b+c)/2;

 2 //s=sqrt(p*(p-a)(p-b)(p-c))

 3 #include<stdio.h>

 4 #include<math.h>

 5 #include<stdlib.h>

 6 int main()

 7 {

 8     double x1,x2,y1,y2,x3,y3;

 9     double a,b,c,p,s;

10     while(~scanf("%lf%lf%lf%lf%lf%lf",&x1,&y1,&x2,&y2,&x3,&y3))

11     {

12         if(x1==0&&y1==0&&x2==0&&y2==0&&x3==0&&y3==0) break; //这个情况不能忽视 

13         a=sqrt(1.0*(x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));

14         b=sqrt(1.0*(x1-x3)*(x1-x3)+(y1-y3)*(y1-y3)); 

15         c=sqrt(1.0*(x3-x2)*(x3-x2)+(y3-y2)*(y3-y2));

16         p=(a+b+c)/2.0;

17         s=sqrt(p*(p-a)*(p-b)*(p-c));

18         printf("%.1lf\n",s);

19     }

20     system("pause");

21     return 0;

22 }

23