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