37 lines
795 B
C++
37 lines
795 B
C++
#include<cstdio>
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#include<cmath>
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#include<algorithm>
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#include<iostream>
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using namespace std;
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struct circle
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{
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double x,y,r;
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};
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double dist(circle a,circle b)
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{
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return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));
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}
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int main()
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{
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circle a,b;
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double d,p,area,sb,sa;
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while(scanf("%lf%lf%lf%lf%lf%lf",&a.x,&a.y,&a.r,&b.x,&b.y,&b.r)!=EOF)
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{
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d=dist(a,b);
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double rr=min(a.r,b.r);
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if(d<=abs(a.r-b.r))
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area=acos(-1.0)*rr*rr;
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else
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if(d>=a.r+b.r)
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area=0.0;
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else{
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p=(a.r+b.r+d)/2.0;
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sa=acos((a.r*a.r+d*d-b.r*b.r)/(2.0*a.r*d));
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sb=acos((b.r*b.r+d*d-a.r*a.r)/(2.0*b.r*d));
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area=sa*a.r*a.r+sb*b.r*b.r-2*sqrt(p*(p-a.r)*(p-b.r)*(p-d));
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}
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printf("%.3lf\n",area);
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}
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return 0;
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}
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