POJ3104_Pie_二分

题目描述

Pie

Time Limit: 1000MS		Memory Limit: 65536K
Total Submissions: 9410		Accepted: 3391		Special Judge

Description


My birthday is coming up and traditionally I'm serving pie. Not just one pie, no, I have a number N of them, of various tastes and of various sizes. F of my friends are
coming to my party and each of them gets a piece of pie. This should be one piece of one pie, not several small pieces since that looks messy. This piece can be one whole pie though. 

My friends are very annoying and if one of them gets a bigger piece than the others, they start complaining. Therefore all of them should get equally sized (but not necessarily equally shaped) pieces, even if this leads to some pie getting spoiled (which is
better than spoiling the party). Of course, I want a piece of pie for myself too, and that piece should also be of the same size. 

What is the largest possible piece size all of us can get? All the pies are cylindrical in shape and they all have the same height 1, but the radii of the pies can be different.
Input

One line with a positive integer: the number of test cases. Then for each test case:
One line with two integers N and F with 1 ≤ N, F ≤ 10 000: the number of pies and the number of friends.
One line with N integers ri with 1 ≤ ri ≤ 10 000: the radii of the pies.

Output

For each test case, output one line with the largest possible volume V such that me and my friends can all get a pie piece of size V. The answer should be given as a floating point number with an absolute error of at most 10−3.
Sample Input

3
3 3
4 3 3
1 24
5
10 5
1 4 2 3 4 5 6 5 4 2

Sample Output

25.1327
3.1416
50.2655

解题报告

切蛋糕，求最大蛋糕的体积。

要求蛋糕需要连续，也就是不能求和平均。。。

数据精度要求偏高。WA了数次竟然是精度没有取够。

代码

#include <iostream>
#include <stdio.h>
#include <cstring>
#include <cmath>
#include <math.h>
#define PI 3.1415926535897932
using namespace std;
bool jud(int *rad,int &n,int &fri,double &mid){
int temp=fri+1;
for(int i=1;i<=n;i++){
temp-=(int)((rad[i]*rad[i])/mid);
}
return temp<=0?true:false;

}
double solve(int *rad,int &n,int &fri){
double mid,r=100000000,l=0;
while(fabs(r-l)>1e-6)
{
mid=(r+l)/2;
if(jud(&rad[0],n,fri,mid))
l=mid;
else
r=mid;

}
return l;
}
int main()
{
int raii[10500];
int test;
int fri,n;
scanf("%d",&test);
for(;test>0;test--)
{
scanf("%d%d",&n,&fri);
for(int i=1;i<=n;i++)
scanf("%d",&raii[i]);
double res=solve(&raii[0],n,fri);
printf("%.4f\n",res*PI);
}
return 0;

}