# POJ 3122 Pie (二分+精度问题)

```#include <iostream>
#include <string.h>
#include <math.h>
#include <queue>
#include <algorithm>
#include <stdlib.h>
#include <map>
#include <set>
#include <stdio.h>
using namespace std;
#define LL __int64
#define pi acos(-1.0)
const int mod=9901;
const int INF=0x3f3f3f3f;
const double eqs=1e-4;
LL v[20000];
bool Judge(double f1, double f2)
{
return f2-f1>eqs;
}
double bin_search(int n, int m)
{
double low=0, high=4e8, mid, ans;
int cnt;
while(Judge(low,high)){
mid=(low+high)/2;
cnt=0;
for(int i=0;i<n;i++){
cnt+=(int)(v[i]*pi/mid);
}
if(cnt>=m){
ans=mid;
low=mid+eqs;
}
else
high=mid-eqs;
}
return ans;
}
int main()
{
int t, n, m, i, r;
scanf("%d",&t);
while(t--){
scanf("%d%d",&n,&m);
m++;
for(i=0;i<n;i++){
scanf("%d",&r);
v[i]=r*r;
}
printf("%.4f\n",bin_search(n,m));
}
return 0;
}
```

POJ 3122 Pie (二分+精度问题)

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