#include <iostream>
#include <cmath>
using namespace std;
int main()
{
	long double x1,x2,x3,y1,y2,y3,a,b,c,perimeter,s,aver;
	while(cin >> x1 >> y1 >> x2 >> y2 >> x3 >> y3)
	{
		a =sqrt( (x1-x2 )*(x1-x2) + (y1-y2)*(y1-y2) );
		b =sqrt( (x1-x3 )*(x1-x3) + (y1-y3)*(y1-y3) );
		c =sqrt( (x3-x2 )*(x3-x2) + (y3-y2)*(y3-y2) );
		aver = (a+b+c) / 2.0 ;
		s = sqrt(  aver*(aver-a)*(aver-b)*(aver-c)  );
		perimeter = 3.141592653589793 * a * b * c / (2 * s);
		cout.setf(ios::fixed);
		cout.precision(2);
		cout << perimeter << endl;
	}
	return 0;
}

• Re:g++ 不能用long double 否则 WA 用double 才可以 c++无所谓 (604) mengfei2011 2013-05-04 14:46:08