水题日记

一定要相信水题真的很水

POJ-2546

#include<iostream>
#include<stdio.h>
#include<cmath>

using namespace std;

#define PI acos(double(-1))

int main()
{
    double x1, y1, r1, x2, y2, r2;
    cin>>x1>>y1>>r1>>x2>>y2>>r2;
    double l = sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));
    double r = r1>r2? r2:r1;
    if(l<=abs(r1-r2))
        printf("%.3lf
",r*r*PI);
    else if(l>=r1+r2)
        printf("%.3lf
",0);
    else
    {
        double ang1 = acos((r1*r1+l*l-r2*r2)/(2*r1*l));
        double ss1 = r1*r1*ang1;
        double ang2 = acos((r2*r2+l*l-r1*r1)/(2*r2*l));
        double ss2 = r2*r2*ang2;
        double s1 = ss1 - r1*sin(ang1)*l/2;
        double s2 = ss2 - r2*sin(ang2)*l/2;
        printf("%.3lf",s1+s2);
    }
    return 0;
}

单纯的靠高中数学就切掉了。