2013
11-11

Circular Area

Your task is to write a program, which, given two circles, calculates the area of their intersection with the accuracy of three digits after decimal point.

In the single line of input file there are space-separated real numbers x1 y1 r1 x2 y2 r2. They represent center coordinates and radii of two circles.

The output file must contain single real number – the area.

20.0 30.0 15.0 40.0 30.0 30.0

608.366


//* @author: ccQ.SuperSupper
import java.io.*;
import java.text.DecimalFormat;
import java.util.*;
import java.math.*;
public class Main {

/**
* @param args
*/
static double min(double a,double b)
{
if(a>b) return b;
return a;
}
static double max(double a,double b)
{
if(a>b) return a;
return b;
}
public static double Number3(double pDouble)
{
String pattern = "##0.###";
DecimalFormat df = new DecimalFormat(pattern);
String result = String.valueOf(df.format(pDouble));
System.out.println(result);
pDouble = Double.parseDouble(result);
return pDouble;
}

public static void main(String[] args)throws Exception {
// TODO Auto-generated method stub
double x1,y1,r1,x2,y2,r2,disten,ans;

Scanner cin = new Scanner(System.in);
while(cin.hasNext()){
x1 = cin.nextDouble();
y1 = cin.nextDouble();
r1 = cin.nextDouble();

x2 = cin.nextDouble();
y2 = cin.nextDouble();
r2 = cin.nextDouble();

disten = Math.sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));

if(disten>=r1+r2){
ans = 0.0;
}
else if(disten+min(r1,r2)<=max(r1,r2)){
ans = Math.acos(-1) * min(r1,r2) * min(r1,r2);
}
else
{
double ans1,ans2;
ans1 = Math.acos((min(r1,r2)*min(r1,r2)+disten*disten-max(r1,r2)*max(r1,r2))/2.0/min(r1,r2)/disten);
ans2 = Math.acos((max(r1,r2)*max(r1,r2)+disten*disten-min(r1,r2)*min(r1,r2))/2.0/max(r1,r2)/disten);
ans = (r1+r2+disten)/2.0;
ans = Math.sqrt(ans*(ans-r1)*(ans-r2)*(ans-disten));
ans = max(r1,r2)*max(r1,r2)*ans2 + min(r1,r2)*min(r1,r2)*ans1 - 2.0*ans;
}
//	ans = Math.floor(ans*1000+0.5)/1000;

DecimalFormat df = new DecimalFormat("##0.000");
System.out.println(df.format(ans));
}
}

}