HDU 6354 E : Everything Has Changed

版权声明：布呗之路的守望者 https://blog.csdn.net/hypHuangYanPing/article/details/81876986

/**
HDU 6354 E : Everything Has Changed
链接:http://acm.hdu.edu.cn/showproblem.php?pid=6354
题意:求所给图案交的周长;
只考虑内切和相交的情况; 用余弦定理定理可以求解;

*/

#include<bits/stdc++.h>
#define pi acos(-1.0)
using namespace std;

int main(){
    int t; cin>>t;
    while(t--){
        int n;double R;
        scanf("%d %lf",&n,&R);
        double ans=2*pi*R;
        while(n--){
            double x,y,r; scanf("%lf %lf %lf",&x,&y,&r);
            if(sqrt(x*x+y*y)+r<R||sqrt(x*x+y*y)>=R+r) continue;
            else if(sqrt(x*x+y*y)+r==R) ans+=2*pi*r;
            else if(sqrt(x*x+y*y)+r>R&&sqrt(x*x+y*y)<(R+r)){
                ans+=(2*r*acos((x*x+y*y+r*r-R*R)/(2*sqrt(x*x+y*y)*r)));//内加;
                ans-=(2*R*acos((x*x+y*y+R*R-r*r)/(2*R*sqrt(x*x+y*y))));//剩余;
            }
        }
        printf("%.7f\n",ans);
    }
    return 0;
}