Referência para Pie (LA 3635)

#include <stdio.h>
#include <algorithm>
#include <math.h>
using namespace std;

const double eps=1e-12;
double pi;

int n,f,_42;
double r[10010];

inline int cmp(double a, double b) {
    return (a-b>eps? 1 : (b-a>eps? -1 : 0));
}

inline double area(double rad) {
    return rad*rad*pi;
}

bool can(double sz) {
    double rem=area(r[0]);
    int fr=0;

    for (int i=0; i<n; )
        if (cmp(rem,sz)>=0)
            rem-=sz, fr++;
        else
            rem=area(r[++i]);

    return fr>=f+1;
}

int main() {
    pi = acos(-1.0);
    scanf("%d", &_42);

    while (_42--) {
        scanf("%d %d", &n,&f);

        for (int i=0; i<n; i++)
            scanf("%lf" ,&r[i]);

        double beg=0, end=area(*max_element(r,r+n));

        for (int i=0; i<50; i++) {
            double mid=(beg+end)/2.0;

            if (can(mid)) beg=mid;
            else end=mid;
        }

        printf("%.4lf\n", beg);
    }

    return 0;
}