HDU - 1724 Ellipse 自适应辛普森模板 - Java

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//Achen

#include<algorithm>

#include<iostream>

#include<cstring>

#include<cstdlib>

#include<cstdio>

#include<cmath>

int T;

double a,b,l,r;

using namespace std;

double f(double x) {

    return b*sqrt(1.0-(x*x)/(a*a));

}

double sim(double x,double y) {

    double mid=((x+y)/2.0);

    return  (y-x)/6.0*(f(x)+4.0*f(mid)+f(y));

}

double calc(double l,double r,double eps) {

    double mid=((l+r)/2.0);

    double tp=sim(l,mid)+sim(mid,r),tpp=sim(l,r);

    if(tp-tpp<=eps*15.0) return tp+(tp-tpp)/15.0;

    else return calc(l,mid,eps/2.0)+calc(mid,r,eps/2.0);

}

int main() {

    scanf("%d",&T);

    while(T--) {

        scanf("%lf%lf%lf%lf",&a,&b,&l,&r);

        printf("%.3lf\n",calc(l,r,1e-)*2.0);

    }

    return ;

}