HDU - 1969 Pie 二分

#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<math.h>
#include<set>
#include<stack>
#include<queue>
#include<ctype.h>
#include<vector>
#include<algorithm>
#define PI acos(-1.0)
// cout << "  ===  " << endl;

using namespace std;
typedef long long ll;
const int maxn = 10000 + 7, INF = 0x3f3f3f3f, mod = 1e9+7;
int T, n, m;
double l, r;
double a[maxn];

void init() {
r = 0.0;
for(int i = 0; i < n; ++i) {
scanf("%lf", &a[i]);
a[i] = a[i] * a[i] * PI;
r = max(r, a[i]);
}
}

void solve() {
l = 0.0;
double mid;
while(l < r - 0.000001) {
int sum = 0;
mid = (l + r) / 2;
for(int i = 0; i < n; ++i)
sum += floor(a[i] / mid);
if(sum >= m)
l = mid;
else r = mid;
}
printf("%.4lf\n", mid);
}

int main() {
scanf("%d", &T);
while(T--) {
scanf("%d %d",&n, &m); m++;
init();
solve();
}
return 0;
}