1439.cpp

这是哈尔滨工业大学acmOJ的源代码

/*  This Code is Submitted by wywcgs for Problem 1439 on 2005-09-18 at 10:44:13 */ 
#include <stdio.h>
#include <math.h>
#define  PI  3.141592653589793

int equal(double, double);

int main()
{
    double x[3], y[3], c;
    double k[2], b[2], cenx, ceny;
    int flag[2], i;
    
    while(scanf("%lf %lf %lf %lf %lf %lf", &x[0], &y[0], &x[1], &y[1], &x[2], &y[2]) == 6) {
        flag[0] = 1;
        flag[1] = 1;
        flag[2] = 1;
        for(i = 0; i < 2; i++) {
            if(!equal(y[0], y[1]) && flag[0]) {
                k[i] = (x[1] - x[0]) / (y[0] - y[1]);
                b[i] = (y[1] + y[0]) / 2 - k[i] * (x[1] + x[0]) / 2;
                flag[0] = 0;
            } else if(!equal(y[1], y[2]) && flag[1]) {
                k[i] = (x[2] - x[1]) / (y[1] - y[2]);
                b[i] = (y[2] + y[1]) / 2 - k[i] * (x[2] + x[1]) / 2;
                flag[1] = 0;
            } else {
                k[i] = (x[2] - x[0]) / (y[0] - y[2]);
                b[i] = (y[2] + y[0]) / 2 - k[i] * (x[2] + x[0]) / 2;
            }    
        }
        cenx = (b[0] - b[1]) / (k[1] - k[0]);
        ceny = k[0] * cenx + b[0];
        c = 2 * PI * sqrt((cenx - x[0])*(cenx - x[0]) + (ceny - y[0])*(ceny - y[0]));
        printf("%.2lf\n", c);
    }

	return 0;
}
int equal(double a, double b)
{
    if(fabs(a-b) < 1e-1) {
        return 1;
    } else {
        return 0;
    }    
}